diff --git a/src/async_impl/client.rs b/src/async_impl/client.rs
index bc0e518dd..0719ba504 100644
--- a/src/async_impl/client.rs
+++ b/src/async_impl/client.rs
@@ -17,7 +17,9 @@ use super::Body;
 use crate::async_impl::h3_client::connect::H3Connector;
 #[cfg(feature = "http3")]
 use crate::async_impl::h3_client::{H3Client, H3ResponseFuture};
-use crate::connect::{Conn, Connector, ConnectorBuilder, ConnectorLayerBuilder, ConnectorService};
+use crate::connect::{
+    BoxedConnectorLayer, BoxedConnectorService, Conn, Connector, ConnectorBuilder,
+};
 #[cfg(feature = "cookies")]
 use crate::cookie;
 #[cfg(feature = "hickory-dns")]
@@ -52,7 +54,8 @@ use quinn::TransportConfig;
 #[cfg(feature = "http3")]
 use quinn::VarInt;
 use tokio::time::Sleep;
-use tower::{layer::util::Stack, Layer, Service, ServiceBuilder};
+use tower::util::BoxCloneSyncServiceLayer;
+use tower::{Layer, Service};
 
 type HyperResponseFuture = hyper_util::client::legacy::ResponseFuture;
 
@@ -76,10 +79,8 @@ pub struct Client {
 
 /// A `ClientBuilder` can be used to create a `Client` with custom configuration.
 #[must_use]
-pub struct ClientBuilder<ConnectorLayers> {
+pub struct ClientBuilder {
     config: Config,
-    // separated out to simplify casting between generic types while copying config
-    connector_layers: ConnectorLayerBuilder<ConnectorLayers>,
 }
 
 enum HttpVersionPref {
@@ -132,6 +133,7 @@ struct Config {
     tls_info: bool,
     #[cfg(feature = "__tls")]
     tls: TlsBackend,
+    connector_layers: Vec<BoxedConnectorLayer>,
     http_version_pref: HttpVersionPref,
     http09_responses: bool,
     http1_title_case_headers: bool,
@@ -177,13 +179,13 @@ struct Config {
     dns_resolver: Option<Arc<dyn Resolve>>,
 }
 
-impl Default for ClientBuilder<tower::layer::util::Identity> {
+impl Default for ClientBuilder {
     fn default() -> Self {
         Self::new()
     }
 }
 
-impl ClientBuilder<tower::layer::util::Identity> {
+impl ClientBuilder {
     /// Constructs a new `ClientBuilder`.
     ///
     /// This is the same as `Client::builder()`.
@@ -235,6 +237,7 @@ impl ClientBuilder<tower::layer::util::Identity> {
                 tls_info: false,
                 #[cfg(feature = "__tls")]
                 tls: TlsBackend::default(),
+                connector_layers: Vec::new(),
                 http_version_pref: HttpVersionPref::All,
                 http09_responses: false,
                 http1_title_case_headers: false,
@@ -278,21 +281,11 @@ impl ClientBuilder<tower::layer::util::Identity> {
                 quic_send_window: None,
                 dns_resolver: None,
             },
-            connector_layers: ConnectorLayerBuilder {
-                builder: ServiceBuilder::new(),
-                has_custom_layers: false,
-            },
         }
     }
 }
 
-impl<ConnectorLayers> ClientBuilder<ConnectorLayers>
-where
-    ConnectorLayers: Layer<ConnectorService>,
-    ConnectorLayers::Service:
-        Service<Uri, Response = Conn, Error = BoxError> + Clone + Send + Sync + 'static,
-    <<ConnectorLayers as Layer<ConnectorService>>::Service as Service<Uri>>::Future: Send + 'static,
-{
+impl ClientBuilder {
     /// Returns a `Client` that uses this `ClientBuilder` configuration.
     ///
     /// # Errors
@@ -815,7 +808,7 @@ where
                     }
                     None => None,
                 },
-                hyper: builder.build(connector_builder.build(self.connector_layers)),
+                hyper: builder.build(connector_builder.build(config.connector_layers)),
                 headers: config.headers,
                 redirect_policy: config.redirect_policy,
                 referer: config.referer,
@@ -850,7 +843,7 @@ where
     /// # Ok(())
     /// # }
     /// ```
-    pub fn user_agent<V>(mut self, value: V) -> ClientBuilder<ConnectorLayers>
+    pub fn user_agent<V>(mut self, value: V) -> ClientBuilder
     where
         V: TryInto<HeaderValue>,
         V::Error: Into<http::Error>,
@@ -888,7 +881,7 @@ where
     /// # Ok(())
     /// # }
     /// ```
-    pub fn default_headers(mut self, headers: HeaderMap) -> ClientBuilder<ConnectorLayers> {
+    pub fn default_headers(mut self, headers: HeaderMap) -> ClientBuilder {
         for (key, value) in headers.iter() {
             self.config.headers.insert(key, value.clone());
         }
@@ -911,7 +904,7 @@ where
     /// This requires the optional `cookies` feature to be enabled.
     #[cfg(feature = "cookies")]
     #[cfg_attr(docsrs, doc(cfg(feature = "cookies")))]
-    pub fn cookie_store(mut self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn cookie_store(mut self, enable: bool) -> ClientBuilder {
         if enable {
             self.cookie_provider(Arc::new(cookie::Jar::default()))
         } else {
@@ -938,7 +931,7 @@ where
     pub fn cookie_provider<C: cookie::CookieStore + 'static>(
         mut self,
         cookie_store: Arc<C>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.config.cookie_store = Some(cookie_store as _);
         self
     }
@@ -961,7 +954,7 @@ where
     /// This requires the optional `gzip` feature to be enabled
     #[cfg(feature = "gzip")]
     #[cfg_attr(docsrs, doc(cfg(feature = "gzip")))]
-    pub fn gzip(mut self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn gzip(mut self, enable: bool) -> ClientBuilder {
         self.config.accepts.gzip = enable;
         self
     }
@@ -984,7 +977,7 @@ where
     /// This requires the optional `brotli` feature to be enabled
     #[cfg(feature = "brotli")]
     #[cfg_attr(docsrs, doc(cfg(feature = "brotli")))]
-    pub fn brotli(mut self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn brotli(mut self, enable: bool) -> ClientBuilder {
         self.config.accepts.brotli = enable;
         self
     }
@@ -1007,7 +1000,7 @@ where
     /// This requires the optional `zstd` feature to be enabled
     #[cfg(feature = "zstd")]
     #[cfg_attr(docsrs, doc(cfg(feature = "zstd")))]
-    pub fn zstd(mut self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn zstd(mut self, enable: bool) -> ClientBuilder {
         self.config.accepts.zstd = enable;
         self
     }
@@ -1030,7 +1023,7 @@ where
     /// This requires the optional `deflate` feature to be enabled
     #[cfg(feature = "deflate")]
     #[cfg_attr(docsrs, doc(cfg(feature = "deflate")))]
-    pub fn deflate(mut self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn deflate(mut self, enable: bool) -> ClientBuilder {
         self.config.accepts.deflate = enable;
         self
     }
@@ -1040,7 +1033,7 @@ where
     /// This method exists even if the optional `gzip` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use gzip decompression
     /// even if another dependency were to enable the optional `gzip` feature.
-    pub fn no_gzip(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_gzip(self) -> ClientBuilder {
         #[cfg(feature = "gzip")]
         {
             self.gzip(false)
@@ -1057,7 +1050,7 @@ where
     /// This method exists even if the optional `brotli` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use brotli decompression
     /// even if another dependency were to enable the optional `brotli` feature.
-    pub fn no_brotli(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_brotli(self) -> ClientBuilder {
         #[cfg(feature = "brotli")]
         {
             self.brotli(false)
@@ -1074,7 +1067,7 @@ where
     /// This method exists even if the optional `zstd` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use zstd decompression
     /// even if another dependency were to enable the optional `zstd` feature.
-    pub fn no_zstd(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_zstd(self) -> ClientBuilder {
         #[cfg(feature = "zstd")]
         {
             self.zstd(false)
@@ -1091,7 +1084,7 @@ where
     /// This method exists even if the optional `deflate` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use deflate decompression
     /// even if another dependency were to enable the optional `deflate` feature.
-    pub fn no_deflate(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_deflate(self) -> ClientBuilder {
         #[cfg(feature = "deflate")]
         {
             self.deflate(false)
@@ -1108,7 +1101,7 @@ where
     /// Set a `RedirectPolicy` for this client.
     ///
     /// Default will follow redirects up to a maximum of 10.
-    pub fn redirect(mut self, policy: redirect::Policy) -> ClientBuilder<ConnectorLayers> {
+    pub fn redirect(mut self, policy: redirect::Policy) -> ClientBuilder {
         self.config.redirect_policy = policy;
         self
     }
@@ -1116,7 +1109,7 @@ where
     /// Enable or disable automatic setting of the `Referer` header.
     ///
     /// Default is `true`.
-    pub fn referer(mut self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn referer(mut self, enable: bool) -> ClientBuilder {
         self.config.referer = enable;
         self
     }
@@ -1128,7 +1121,7 @@ where
     /// # Note
     ///
     /// Adding a proxy will disable the automatic usage of the "system" proxy.
-    pub fn proxy(mut self, proxy: Proxy) -> ClientBuilder<ConnectorLayers> {
+    pub fn proxy(mut self, proxy: Proxy) -> ClientBuilder {
         self.config.proxies.push(proxy);
         self.config.auto_sys_proxy = false;
         self
@@ -1141,7 +1134,7 @@ where
     /// on all desired proxies instead.
     ///
     /// This also disables the automatic usage of the "system" proxy.
-    pub fn no_proxy(mut self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_proxy(mut self) -> ClientBuilder {
         self.config.proxies.clear();
         self.config.auto_sys_proxy = false;
         self
@@ -1155,7 +1148,7 @@ where
     /// response body has finished. Also considered a total deadline.
     ///
     /// Default is no timeout.
-    pub fn timeout(mut self, timeout: Duration) -> ClientBuilder<ConnectorLayers> {
+    pub fn timeout(mut self, timeout: Duration) -> ClientBuilder {
         self.config.timeout = Some(timeout);
         self
     }
@@ -1167,7 +1160,7 @@ where
     /// connections when the size isn't known beforehand.
     ///
     /// Default is no timeout.
-    pub fn read_timeout(mut self, timeout: Duration) -> ClientBuilder<ConnectorLayers> {
+    pub fn read_timeout(mut self, timeout: Duration) -> ClientBuilder {
         self.config.read_timeout = Some(timeout);
         self
     }
@@ -1180,7 +1173,7 @@ where
     ///
     /// This **requires** the futures be executed in a tokio runtime with
     /// a tokio timer enabled.
-    pub fn connect_timeout(mut self, timeout: Duration) -> ClientBuilder<ConnectorLayers> {
+    pub fn connect_timeout(mut self, timeout: Duration) -> ClientBuilder {
         self.config.connect_timeout = Some(timeout);
         self
     }
@@ -1191,7 +1184,7 @@ where
     /// for read and write operations on connections.
     ///
     /// [log]: https://crates.io/crates/log
-    pub fn connection_verbose(mut self, verbose: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn connection_verbose(mut self, verbose: bool) -> ClientBuilder {
         self.config.connection_verbose = verbose;
         self
     }
@@ -1203,7 +1196,7 @@ where
     /// Pass `None` to disable timeout.
     ///
     /// Default is 90 seconds.
-    pub fn pool_idle_timeout<D>(mut self, val: D) -> ClientBuilder<ConnectorLayers>
+    pub fn pool_idle_timeout<D>(mut self, val: D) -> ClientBuilder
     where
         D: Into<Option<Duration>>,
     {
@@ -1212,13 +1205,13 @@ where
     }
 
     /// Sets the maximum idle connection per host allowed in the pool.
-    pub fn pool_max_idle_per_host(mut self, max: usize) -> ClientBuilder<ConnectorLayers> {
+    pub fn pool_max_idle_per_host(mut self, max: usize) -> ClientBuilder {
         self.config.pool_max_idle_per_host = max;
         self
     }
 
     /// Send headers as title case instead of lowercase.
-    pub fn http1_title_case_headers(mut self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http1_title_case_headers(mut self) -> ClientBuilder {
         self.config.http1_title_case_headers = true;
         self
     }
@@ -1231,17 +1224,14 @@ where
     pub fn http1_allow_obsolete_multiline_headers_in_responses(
         mut self,
         value: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.config
             .http1_allow_obsolete_multiline_headers_in_responses = value;
         self
     }
 
     /// Sets whether invalid header lines should be silently ignored in HTTP/1 responses.
-    pub fn http1_ignore_invalid_headers_in_responses(
-        mut self,
-        value: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http1_ignore_invalid_headers_in_responses(mut self, value: bool) -> ClientBuilder {
         self.config.http1_ignore_invalid_headers_in_responses = value;
         self
     }
@@ -1254,20 +1244,20 @@ where
     pub fn http1_allow_spaces_after_header_name_in_responses(
         mut self,
         value: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.config
             .http1_allow_spaces_after_header_name_in_responses = value;
         self
     }
 
     /// Only use HTTP/1.
-    pub fn http1_only(mut self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http1_only(mut self) -> ClientBuilder {
         self.config.http_version_pref = HttpVersionPref::Http1;
         self
     }
 
     /// Allow HTTP/0.9 responses
-    pub fn http09_responses(mut self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http09_responses(mut self) -> ClientBuilder {
         self.config.http09_responses = true;
         self
     }
@@ -1275,7 +1265,7 @@ where
     /// Only use HTTP/2.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_prior_knowledge(mut self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_prior_knowledge(mut self) -> ClientBuilder {
         self.config.http_version_pref = HttpVersionPref::Http2;
         self
     }
@@ -1283,7 +1273,7 @@ where
     /// Only use HTTP/3.
     #[cfg(feature = "http3")]
     #[cfg_attr(docsrs, doc(cfg(all(reqwest_unstable, feature = "http3",))))]
-    pub fn http3_prior_knowledge(mut self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http3_prior_knowledge(mut self) -> ClientBuilder {
         self.config.http_version_pref = HttpVersionPref::Http3;
         self
     }
@@ -1293,10 +1283,7 @@ where
     /// Default is currently 65,535 but may change internally to optimize for common uses.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_initial_stream_window_size(
-        mut self,
-        sz: impl Into<Option<u32>>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_initial_stream_window_size(mut self, sz: impl Into<Option<u32>>) -> ClientBuilder {
         self.config.http2_initial_stream_window_size = sz.into();
         self
     }
@@ -1309,7 +1296,7 @@ where
     pub fn http2_initial_connection_window_size(
         mut self,
         sz: impl Into<Option<u32>>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.config.http2_initial_connection_window_size = sz.into();
         self
     }
@@ -1320,7 +1307,7 @@ where
     /// `http2_initial_connection_window_size`.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_adaptive_window(mut self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_adaptive_window(mut self, enabled: bool) -> ClientBuilder {
         self.config.http2_adaptive_window = enabled;
         self
     }
@@ -1330,10 +1317,7 @@ where
     /// Default is currently 16,384 but may change internally to optimize for common uses.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_max_frame_size(
-        mut self,
-        sz: impl Into<Option<u32>>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_max_frame_size(mut self, sz: impl Into<Option<u32>>) -> ClientBuilder {
         self.config.http2_max_frame_size = sz.into();
         self
     }
@@ -1343,10 +1327,7 @@ where
     /// Default is currently 16KB, but can change.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_max_header_list_size(
-        mut self,
-        max_header_size_bytes: u32,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_max_header_list_size(mut self, max_header_size_bytes: u32) -> ClientBuilder {
         self.config.http2_max_header_list_size = Some(max_header_size_bytes);
         self
     }
@@ -1360,7 +1341,7 @@ where
     pub fn http2_keep_alive_interval(
         mut self,
         interval: impl Into<Option<Duration>>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.config.http2_keep_alive_interval = interval.into();
         self
     }
@@ -1372,7 +1353,7 @@ where
     /// Default is currently disabled.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_keep_alive_timeout(mut self, timeout: Duration) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_keep_alive_timeout(mut self, timeout: Duration) -> ClientBuilder {
         self.config.http2_keep_alive_timeout = Some(timeout);
         self
     }
@@ -1385,7 +1366,7 @@ where
     /// Default is `false`.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_keep_alive_while_idle(mut self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_keep_alive_while_idle(mut self, enabled: bool) -> ClientBuilder {
         self.config.http2_keep_alive_while_idle = enabled;
         self
     }
@@ -1395,7 +1376,7 @@ where
     /// Set whether sockets have `TCP_NODELAY` enabled.
     ///
     /// Default is `true`.
-    pub fn tcp_nodelay(mut self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tcp_nodelay(mut self, enabled: bool) -> ClientBuilder {
         self.config.nodelay = enabled;
         self
     }
@@ -1413,7 +1394,7 @@ where
     ///     .local_address(local_addr)
     ///     .build().unwrap();
     /// ```
-    pub fn local_address<T>(mut self, addr: T) -> ClientBuilder<ConnectorLayers>
+    pub fn local_address<T>(mut self, addr: T) -> ClientBuilder
     where
         T: Into<Option<IpAddr>>,
     {
@@ -1434,7 +1415,7 @@ where
     ///     .build().unwrap();
     /// ```
     #[cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux"))]
-    pub fn interface(mut self, interface: &str) -> ClientBuilder<ConnectorLayers> {
+    pub fn interface(mut self, interface: &str) -> ClientBuilder {
         self.config.interface = Some(interface.to_string());
         self
     }
@@ -1442,7 +1423,7 @@ where
     /// Set that all sockets have `SO_KEEPALIVE` set with the supplied duration.
     ///
     /// If `None`, the option will not be set.
-    pub fn tcp_keepalive<D>(mut self, val: D) -> ClientBuilder<ConnectorLayers>
+    pub fn tcp_keepalive<D>(mut self, val: D) -> ClientBuilder
     where
         D: Into<Option<Duration>>,
     {
@@ -1470,7 +1451,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn add_root_certificate(mut self, cert: Certificate) -> ClientBuilder<ConnectorLayers> {
+    pub fn add_root_certificate(mut self, cert: Certificate) -> ClientBuilder {
         self.config.root_certs.push(cert);
         self
     }
@@ -1483,7 +1464,7 @@ where
     /// This requires the `rustls-tls(-...)` Cargo feature enabled.
     #[cfg(feature = "__rustls")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls")))]
-    pub fn add_crl(mut self, crl: CertificateRevocationList) -> ClientBuilder<ConnectorLayers> {
+    pub fn add_crl(mut self, crl: CertificateRevocationList) -> ClientBuilder {
         self.config.crls.push(crl);
         self
     }
@@ -1499,7 +1480,7 @@ where
     pub fn add_crls(
         mut self,
         crls: impl IntoIterator<Item = CertificateRevocationList>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.config.crls.extend(crls);
         self
     }
@@ -1530,10 +1511,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn tls_built_in_root_certs(
-        mut self,
-        tls_built_in_root_certs: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_built_in_root_certs(mut self, tls_built_in_root_certs: bool) -> ClientBuilder {
         self.config.tls_built_in_root_certs = tls_built_in_root_certs;
 
         #[cfg(feature = "rustls-tls-webpki-roots-no-provider")]
@@ -1554,7 +1532,7 @@ where
     /// If the feature is enabled, this value is `true` by default.
     #[cfg(feature = "rustls-tls-webpki-roots-no-provider")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls-webpki-roots-no-provider")))]
-    pub fn tls_built_in_webpki_certs(mut self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_built_in_webpki_certs(mut self, enabled: bool) -> ClientBuilder {
         self.config.tls_built_in_certs_webpki = enabled;
         self
     }
@@ -1564,7 +1542,7 @@ where
     /// If the feature is enabled, this value is `true` by default.
     #[cfg(feature = "rustls-tls-native-roots-no-provider")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls-native-roots-no-provider")))]
-    pub fn tls_built_in_native_certs(mut self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_built_in_native_certs(mut self, enabled: bool) -> ClientBuilder {
         self.config.tls_built_in_certs_native = enabled;
         self
     }
@@ -1577,7 +1555,7 @@ where
     /// enabled.
     #[cfg(any(feature = "native-tls", feature = "__rustls"))]
     #[cfg_attr(docsrs, doc(cfg(any(feature = "native-tls", feature = "rustls-tls"))))]
-    pub fn identity(mut self, identity: Identity) -> ClientBuilder<ConnectorLayers> {
+    pub fn identity(mut self, identity: Identity) -> ClientBuilder {
         self.config.identity = Some(identity);
         self
     }
@@ -1609,7 +1587,7 @@ where
     pub fn danger_accept_invalid_hostnames(
         mut self,
         accept_invalid_hostname: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.config.hostname_verification = !accept_invalid_hostname;
         self
     }
@@ -1639,10 +1617,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn danger_accept_invalid_certs(
-        mut self,
-        accept_invalid_certs: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn danger_accept_invalid_certs(mut self, accept_invalid_certs: bool) -> ClientBuilder {
         self.config.certs_verification = !accept_invalid_certs;
         self
     }
@@ -1664,7 +1639,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn tls_sni(mut self, tls_sni: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_sni(mut self, tls_sni: bool) -> ClientBuilder {
         self.config.tls_sni = tls_sni;
         self
     }
@@ -1693,7 +1668,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn min_tls_version(mut self, version: tls::Version) -> ClientBuilder<ConnectorLayers> {
+    pub fn min_tls_version(mut self, version: tls::Version) -> ClientBuilder {
         self.config.min_tls_version = Some(version);
         self
     }
@@ -1725,7 +1700,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn max_tls_version(mut self, version: tls::Version) -> ClientBuilder<ConnectorLayers> {
+    pub fn max_tls_version(mut self, version: tls::Version) -> ClientBuilder {
         self.config.max_tls_version = Some(version);
         self
     }
@@ -1740,7 +1715,7 @@ where
     /// This requires the optional `native-tls` feature to be enabled.
     #[cfg(feature = "native-tls")]
     #[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
-    pub fn use_native_tls(mut self) -> ClientBuilder<ConnectorLayers> {
+    pub fn use_native_tls(mut self) -> ClientBuilder {
         self.config.tls = TlsBackend::Default;
         self
     }
@@ -1755,7 +1730,7 @@ where
     /// This requires the optional `rustls-tls(-...)` feature to be enabled.
     #[cfg(feature = "__rustls")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls")))]
-    pub fn use_rustls_tls(mut self) -> ClientBuilder<ConnectorLayers> {
+    pub fn use_rustls_tls(mut self) -> ClientBuilder {
         self.config.tls = TlsBackend::Rustls;
         self
     }
@@ -1780,7 +1755,7 @@ where
     /// `rustls-tls(-...)` to be enabled.
     #[cfg(any(feature = "native-tls", feature = "__rustls",))]
     #[cfg_attr(docsrs, doc(cfg(any(feature = "native-tls", feature = "rustls-tls"))))]
-    pub fn use_preconfigured_tls(mut self, tls: impl Any) -> ClientBuilder<ConnectorLayers> {
+    pub fn use_preconfigured_tls(mut self, tls: impl Any) -> ClientBuilder {
         let mut tls = Some(tls);
         #[cfg(feature = "native-tls")]
         {
@@ -1823,7 +1798,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn tls_info(mut self, tls_info: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_info(mut self, tls_info: bool) -> ClientBuilder {
         self.config.tls_info = tls_info;
         self
     }
@@ -1831,7 +1806,7 @@ where
     /// Restrict the Client to be used with HTTPS only requests.
     ///
     /// Defaults to false.
-    pub fn https_only(mut self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn https_only(mut self, enabled: bool) -> ClientBuilder {
         self.config.https_only = enabled;
         self
     }
@@ -1840,7 +1815,7 @@ where
     #[cfg(feature = "hickory-dns")]
     #[cfg_attr(docsrs, doc(cfg(feature = "hickory-dns")))]
     #[deprecated(note = "use `hickory_dns` instead")]
-    pub fn trust_dns(mut self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn trust_dns(mut self, enable: bool) -> ClientBuilder {
         self.config.hickory_dns = enable;
         self
     }
@@ -1860,14 +1835,14 @@ where
     /// that the default resolver does
     #[cfg(feature = "hickory-dns")]
     #[cfg_attr(docsrs, doc(cfg(feature = "hickory-dns")))]
-    pub fn hickory_dns(mut self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn hickory_dns(mut self, enable: bool) -> ClientBuilder {
         self.config.hickory_dns = enable;
         self
     }
 
     #[doc(hidden)]
     #[deprecated(note = "use `no_hickory_dns` instead")]
-    pub fn no_trust_dns(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_trust_dns(self) -> ClientBuilder {
         self.no_hickory_dns()
     }
 
@@ -1876,7 +1851,7 @@ where
     /// This method exists even if the optional `hickory-dns` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use the hickory-dns async resolver
     /// even if another dependency were to enable the optional `hickory-dns` feature.
-    pub fn no_hickory_dns(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_hickory_dns(self) -> ClientBuilder {
         #[cfg(feature = "hickory-dns")]
         {
             self.hickory_dns(false)
@@ -1892,7 +1867,7 @@ where
     ///
     /// Set the port to `0` to use the conventional port for the given scheme (e.g. 80 for http).
     /// Ports in the URL itself will always be used instead of the port in the overridden addr.
-    pub fn resolve(self, domain: &str, addr: SocketAddr) -> ClientBuilder<ConnectorLayers> {
+    pub fn resolve(self, domain: &str, addr: SocketAddr) -> ClientBuilder {
         self.resolve_to_addrs(domain, &[addr])
     }
 
@@ -1900,11 +1875,7 @@ where
     ///
     /// Set the port to `0` to use the conventional port for the given scheme (e.g. 80 for http).
     /// Ports in the URL itself will always be used instead of the port in the overridden addr.
-    pub fn resolve_to_addrs(
-        mut self,
-        domain: &str,
-        addrs: &[SocketAddr],
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn resolve_to_addrs(mut self, domain: &str, addrs: &[SocketAddr]) -> ClientBuilder {
         self.config
             .dns_overrides
             .insert(domain.to_ascii_lowercase(), addrs.to_vec());
@@ -1916,10 +1887,7 @@ where
     /// Pass an `Arc` wrapping a trait object implementing `Resolve`.
     /// Overrides for specific names passed to `resolve` and `resolve_to_addrs` will
     /// still be applied on top of this resolver.
-    pub fn dns_resolver<R: Resolve + 'static>(
-        mut self,
-        resolver: Arc<R>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn dns_resolver<R: Resolve + 'static>(mut self, resolver: Arc<R>) -> ClientBuilder {
         self.config.dns_resolver = Some(resolver as _);
         self
     }
@@ -1930,7 +1898,7 @@ where
     /// The default is false.
     #[cfg(feature = "http3")]
     #[cfg_attr(docsrs, doc(cfg(all(reqwest_unstable, feature = "http3",))))]
-    pub fn tls_early_data(mut self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_early_data(mut self, enabled: bool) -> ClientBuilder {
         self.config.tls_enable_early_data = enabled;
         self
     }
@@ -1942,7 +1910,7 @@ where
     /// [`TransportConfig`]: https://docs.rs/quinn/latest/quinn/struct.TransportConfig.html
     #[cfg(feature = "http3")]
     #[cfg_attr(docsrs, doc(cfg(all(reqwest_unstable, feature = "http3",))))]
-    pub fn http3_max_idle_timeout(mut self, value: Duration) -> ClientBuilder<ConnectorLayers> {
+    pub fn http3_max_idle_timeout(mut self, value: Duration) -> ClientBuilder {
         self.config.quic_max_idle_timeout = Some(value);
         self
     }
@@ -1959,7 +1927,7 @@ where
     /// Panics if the value is over 2^62.
     #[cfg(feature = "http3")]
     #[cfg_attr(docsrs, doc(cfg(all(reqwest_unstable, feature = "http3",))))]
-    pub fn http3_stream_receive_window(mut self, value: u64) -> ClientBuilder<ConnectorLayers> {
+    pub fn http3_stream_receive_window(mut self, value: u64) -> ClientBuilder {
         self.config.quic_stream_receive_window = Some(value.try_into().unwrap());
         self
     }
@@ -1976,7 +1944,7 @@ where
     /// Panics if the value is over 2^62.
     #[cfg(feature = "http3")]
     #[cfg_attr(docsrs, doc(cfg(all(reqwest_unstable, feature = "http3",))))]
-    pub fn http3_conn_receive_window(mut self, value: u64) -> ClientBuilder<ConnectorLayers> {
+    pub fn http3_conn_receive_window(mut self, value: u64) -> ClientBuilder {
         self.config.quic_receive_window = Some(value.try_into().unwrap());
         self
     }
@@ -1988,49 +1956,45 @@ where
     /// [`TransportConfig`]: https://docs.rs/quinn/latest/quinn/struct.TransportConfig.html
     #[cfg(feature = "http3")]
     #[cfg_attr(docsrs, doc(cfg(all(reqwest_unstable, feature = "http3",))))]
-    pub fn http3_send_window(mut self, value: u64) -> ClientBuilder<ConnectorLayers> {
+    pub fn http3_send_window(mut self, value: u64) -> ClientBuilder {
         self.config.quic_send_window = Some(value);
         self
     }
 
     /// Adds a new Tower [`Layer`](https://docs.rs/tower/latest/tower/trait.Layer.html) to the
     /// base connector [`Service`](https://docs.rs/tower/latest/tower/trait.Service.html) which
-    /// is responsible for connection establishment.
+    /// is responsible for connection establishment.a
     ///
     /// Each subsequent invocation of this function will wrap previous layers.
     ///
     /// If configured, the `connect_timeout` will be the outermost layer.
     ///
-    /// Simple example:
+    /// Example usage:
     /// ```
     /// use std::time::Duration;
     ///
     /// # #[cfg(not(feature = "rustls-tls-no-provider"))]
     /// let client = reqwest::Client::builder()
-    ///                      // resolved to outermost layer, so before the semaphore permit is attempted
-    ///                      .connect_timeout(Duration::from_millis(100))
-    ///                      // underneath the concurrency check, so only after a semaphore permit is acquired
+    ///                      // resolved to outermost layer, meaning while we are waiting on concurrency limit
+    ///                      .connect_timeout(Duration::from_millis(200))
+    ///                      // underneath the concurrency check, so only after concurrency limit lets us through
     ///                      .connector_layer(tower::timeout::TimeoutLayer::new(Duration::from_millis(50)))
     ///                      .connector_layer(tower::limit::concurrency::ConcurrencyLimitLayer::new(2))
     ///                      .build()
     ///                      .unwrap();
     /// ```
     ///
-    /// For a more complex example involving a custom layer, see `examples/connect_via_lower_priority_tokio_runtime.rs`.
-    pub fn connector_layer<S, L>(self, layer: L) -> ClientBuilder<Stack<L, ConnectorLayers>>
+    pub fn connector_layer<L>(mut self, layer: L) -> ClientBuilder
     where
-        S: Send + Sync + Clone + 'static,
-        L: Layer<ConnectorLayers, Service = S> + Send + Sync + Clone + 'static,
+        L: Layer<BoxedConnectorService> + Clone + Send + Sync + 'static,
+        L::Service: Service<Uri, Response = Conn, Error = BoxError> + Clone + Send + Sync + 'static,
+        <L::Service as Service<Uri>>::Future: Send + 'static,
     {
-        let connector_layers = ConnectorLayerBuilder {
-            builder: self.connector_layers.builder.layer(layer),
-            has_custom_layers: true,
-        };
+        let layer = BoxCloneSyncServiceLayer::new(layer);
 
-        ClientBuilder::<Stack<L, ConnectorLayers>> {
-            config: self.config,
-            connector_layers,
-        }
+        self.config.connector_layers.push(layer);
+
+        self
     }
 }
 
@@ -2059,7 +2023,7 @@ impl Client {
     /// Creates a `ClientBuilder` to configure a `Client`.
     ///
     /// This is the same as `ClientBuilder::new()`.
-    pub fn builder() -> ClientBuilder<tower::layer::util::Identity> {
+    pub fn builder() -> ClientBuilder {
         ClientBuilder::new()
     }
 
@@ -2316,7 +2280,7 @@ impl tower_service::Service<Request> for &'_ Client {
     }
 }
 
-impl<ConnectorLayers> fmt::Debug for ClientBuilder<ConnectorLayers> {
+impl fmt::Debug for ClientBuilder {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let mut builder = f.debug_struct("ClientBuilder");
         self.config.fmt_fields(&mut builder);
diff --git a/src/blocking/client.rs b/src/blocking/client.rs
index 5279d47f3..4ac51602b 100644
--- a/src/blocking/client.rs
+++ b/src/blocking/client.rs
@@ -13,15 +13,14 @@ use http::header::HeaderValue;
 use http::Uri;
 use log::{error, trace};
 use tokio::sync::{mpsc, oneshot};
-use tower::layer::util::Stack;
 use tower::Layer;
 use tower::Service;
 
 use super::request::{Request, RequestBuilder};
 use super::response::Response;
 use super::wait;
+use crate::connect::BoxedConnectorService;
 use crate::connect::Conn;
-use crate::connect::ConnectorService;
 use crate::dns::Resolve;
 use crate::error::BoxError;
 #[cfg(feature = "__tls")]
@@ -76,18 +75,18 @@ pub struct Client {
 /// # }
 /// ```
 #[must_use]
-pub struct ClientBuilder<ConnectorLayers> {
-    inner: async_impl::ClientBuilder<ConnectorLayers>,
+pub struct ClientBuilder {
+    inner: async_impl::ClientBuilder,
     timeout: Timeout,
 }
 
-impl Default for ClientBuilder<tower::layer::util::Identity> {
+impl Default for ClientBuilder {
     fn default() -> Self {
         Self::new()
     }
 }
 
-impl ClientBuilder<tower::layer::util::Identity> {
+impl ClientBuilder {
     /// Constructs a new `ClientBuilder`.
     ///
     /// This is the same as `Client::builder()`.
@@ -99,13 +98,7 @@ impl ClientBuilder<tower::layer::util::Identity> {
     }
 }
 
-impl<ConnectorLayers> ClientBuilder<ConnectorLayers>
-where
-    ConnectorLayers: Layer<ConnectorService> + Send + Sync + 'static,
-    ConnectorLayers::Service:
-        Service<Uri, Response = Conn, Error = BoxError> + Clone + Send + Sync + 'static,
-    <<ConnectorLayers as Layer<ConnectorService>>::Service as Service<Uri>>::Future: Send + 'static,
-{
+impl ClientBuilder {
     /// Returns a `Client` that uses this `ClientBuilder` configuration.
     ///
     /// # Errors
@@ -143,7 +136,7 @@ where
     /// # Ok(())
     /// # }
     /// ```
-    pub fn user_agent<V>(self, value: V) -> ClientBuilder<ConnectorLayers>
+    pub fn user_agent<V>(self, value: V) -> ClientBuilder
     where
         V: TryInto<HeaderValue>,
         V::Error: Into<http::Error>,
@@ -175,7 +168,7 @@ where
     /// # Ok(())
     /// # }
     /// ```
-    pub fn default_headers(self, headers: header::HeaderMap) -> ClientBuilder<ConnectorLayers> {
+    pub fn default_headers(self, headers: header::HeaderMap) -> ClientBuilder {
         self.with_inner(move |inner| inner.default_headers(headers))
     }
 
@@ -191,7 +184,7 @@ where
     /// This requires the optional `cookies` feature to be enabled.
     #[cfg(feature = "cookies")]
     #[cfg_attr(docsrs, doc(cfg(feature = "cookies")))]
-    pub fn cookie_store(self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn cookie_store(self, enable: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.cookie_store(enable))
     }
 
@@ -210,7 +203,7 @@ where
     pub fn cookie_provider<C: crate::cookie::CookieStore + 'static>(
         self,
         cookie_store: Arc<C>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.with_inner(|inner| inner.cookie_provider(cookie_store))
     }
 
@@ -232,7 +225,7 @@ where
     /// This requires the optional `gzip` feature to be enabled
     #[cfg(feature = "gzip")]
     #[cfg_attr(docsrs, doc(cfg(feature = "gzip")))]
-    pub fn gzip(self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn gzip(self, enable: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.gzip(enable))
     }
 
@@ -254,7 +247,7 @@ where
     /// This requires the optional `brotli` feature to be enabled
     #[cfg(feature = "brotli")]
     #[cfg_attr(docsrs, doc(cfg(feature = "brotli")))]
-    pub fn brotli(self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn brotli(self, enable: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.brotli(enable))
     }
 
@@ -276,7 +269,7 @@ where
     /// This requires the optional `zstd` feature to be enabled
     #[cfg(feature = "zstd")]
     #[cfg_attr(docsrs, doc(cfg(feature = "zstd")))]
-    pub fn zstd(self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn zstd(self, enable: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.zstd(enable))
     }
 
@@ -298,7 +291,7 @@ where
     /// This requires the optional `deflate` feature to be enabled
     #[cfg(feature = "deflate")]
     #[cfg_attr(docsrs, doc(cfg(feature = "deflate")))]
-    pub fn deflate(self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn deflate(self, enable: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.deflate(enable))
     }
 
@@ -307,7 +300,7 @@ where
     /// This method exists even if the optional `gzip` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use gzip decompression
     /// even if another dependency were to enable the optional `gzip` feature.
-    pub fn no_gzip(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_gzip(self) -> ClientBuilder {
         self.with_inner(|inner| inner.no_gzip())
     }
 
@@ -316,7 +309,7 @@ where
     /// This method exists even if the optional `brotli` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use brotli decompression
     /// even if another dependency were to enable the optional `brotli` feature.
-    pub fn no_brotli(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_brotli(self) -> ClientBuilder {
         self.with_inner(|inner| inner.no_brotli())
     }
 
@@ -325,7 +318,7 @@ where
     /// This method exists even if the optional `zstd` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use zstd decompression
     /// even if another dependency were to enable the optional `zstd` feature.
-    pub fn no_zstd(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_zstd(self) -> ClientBuilder {
         self.with_inner(|inner| inner.no_zstd())
     }
 
@@ -334,7 +327,7 @@ where
     /// This method exists even if the optional `deflate` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use deflate decompression
     /// even if another dependency were to enable the optional `deflate` feature.
-    pub fn no_deflate(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_deflate(self) -> ClientBuilder {
         self.with_inner(|inner| inner.no_deflate())
     }
 
@@ -343,14 +336,14 @@ where
     /// Set a `redirect::Policy` for this client.
     ///
     /// Default will follow redirects up to a maximum of 10.
-    pub fn redirect(self, policy: redirect::Policy) -> ClientBuilder<ConnectorLayers> {
+    pub fn redirect(self, policy: redirect::Policy) -> ClientBuilder {
         self.with_inner(move |inner| inner.redirect(policy))
     }
 
     /// Enable or disable automatic setting of the `Referer` header.
     ///
     /// Default is `true`.
-    pub fn referer(self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn referer(self, enable: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.referer(enable))
     }
 
@@ -361,7 +354,7 @@ where
     /// # Note
     ///
     /// Adding a proxy will disable the automatic usage of the "system" proxy.
-    pub fn proxy(self, proxy: Proxy) -> ClientBuilder<ConnectorLayers> {
+    pub fn proxy(self, proxy: Proxy) -> ClientBuilder {
         self.with_inner(move |inner| inner.proxy(proxy))
     }
 
@@ -372,7 +365,7 @@ where
     /// on all desired proxies instead.
     ///
     /// This also disables the automatic usage of the "system" proxy.
-    pub fn no_proxy(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_proxy(self) -> ClientBuilder {
         self.with_inner(move |inner| inner.no_proxy())
     }
 
@@ -383,7 +376,7 @@ where
     /// Default is 30 seconds.
     ///
     /// Pass `None` to disable timeout.
-    pub fn timeout<T>(mut self, timeout: T) -> ClientBuilder<ConnectorLayers>
+    pub fn timeout<T>(mut self, timeout: T) -> ClientBuilder
     where
         T: Into<Option<Duration>>,
     {
@@ -394,7 +387,7 @@ where
     /// Set a timeout for only the connect phase of a `Client`.
     ///
     /// Default is `None`.
-    pub fn connect_timeout<T>(self, timeout: T) -> ClientBuilder<ConnectorLayers>
+    pub fn connect_timeout<T>(self, timeout: T) -> ClientBuilder
     where
         T: Into<Option<Duration>>,
     {
@@ -412,7 +405,7 @@ where
     /// for read and write operations on connections.
     ///
     /// [log]: https://crates.io/crates/log
-    pub fn connection_verbose(self, verbose: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn connection_verbose(self, verbose: bool) -> ClientBuilder {
         self.with_inner(move |inner| inner.connection_verbose(verbose))
     }
 
@@ -423,7 +416,7 @@ where
     /// Pass `None` to disable timeout.
     ///
     /// Default is 90 seconds.
-    pub fn pool_idle_timeout<D>(self, val: D) -> ClientBuilder<ConnectorLayers>
+    pub fn pool_idle_timeout<D>(self, val: D) -> ClientBuilder
     where
         D: Into<Option<Duration>>,
     {
@@ -431,12 +424,12 @@ where
     }
 
     /// Sets the maximum idle connection per host allowed in the pool.
-    pub fn pool_max_idle_per_host(self, max: usize) -> ClientBuilder<ConnectorLayers> {
+    pub fn pool_max_idle_per_host(self, max: usize) -> ClientBuilder {
         self.with_inner(move |inner| inner.pool_max_idle_per_host(max))
     }
 
     /// Send headers as title case instead of lowercase.
-    pub fn http1_title_case_headers(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http1_title_case_headers(self) -> ClientBuilder {
         self.with_inner(|inner| inner.http1_title_case_headers())
     }
 
@@ -445,18 +438,12 @@ where
     ///
     /// Newline codepoints (`\r` and `\n`) will be transformed to spaces when
     /// parsing.
-    pub fn http1_allow_obsolete_multiline_headers_in_responses(
-        self,
-        value: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http1_allow_obsolete_multiline_headers_in_responses(self, value: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.http1_allow_obsolete_multiline_headers_in_responses(value))
     }
 
     /// Sets whether invalid header lines should be silently ignored in HTTP/1 responses.
-    pub fn http1_ignore_invalid_headers_in_responses(
-        self,
-        value: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http1_ignore_invalid_headers_in_responses(self, value: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.http1_ignore_invalid_headers_in_responses(value))
     }
 
@@ -465,27 +452,24 @@ where
     ///
     /// Newline codepoints (\r and \n) will be transformed to spaces when
     /// parsing.
-    pub fn http1_allow_spaces_after_header_name_in_responses(
-        self,
-        value: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http1_allow_spaces_after_header_name_in_responses(self, value: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.http1_allow_spaces_after_header_name_in_responses(value))
     }
 
     /// Only use HTTP/1.
-    pub fn http1_only(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http1_only(self) -> ClientBuilder {
         self.with_inner(|inner| inner.http1_only())
     }
 
     /// Allow HTTP/0.9 responses
-    pub fn http09_responses(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http09_responses(self) -> ClientBuilder {
         self.with_inner(|inner| inner.http09_responses())
     }
 
     /// Only use HTTP/2.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_prior_knowledge(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_prior_knowledge(self) -> ClientBuilder {
         self.with_inner(|inner| inner.http2_prior_knowledge())
     }
 
@@ -494,10 +478,7 @@ where
     /// Default is currently 65,535 but may change internally to optimize for common uses.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_initial_stream_window_size(
-        self,
-        sz: impl Into<Option<u32>>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_initial_stream_window_size(self, sz: impl Into<Option<u32>>) -> ClientBuilder {
         self.with_inner(|inner| inner.http2_initial_stream_window_size(sz))
     }
 
@@ -506,10 +487,7 @@ where
     /// Default is currently 65,535 but may change internally to optimize for common uses.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_initial_connection_window_size(
-        self,
-        sz: impl Into<Option<u32>>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_initial_connection_window_size(self, sz: impl Into<Option<u32>>) -> ClientBuilder {
         self.with_inner(|inner| inner.http2_initial_connection_window_size(sz))
     }
 
@@ -519,7 +497,7 @@ where
     /// `http2_initial_connection_window_size`.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_adaptive_window(self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_adaptive_window(self, enabled: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.http2_adaptive_window(enabled))
     }
 
@@ -528,10 +506,7 @@ where
     /// Default is currently 16,384 but may change internally to optimize for common uses.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_max_frame_size(
-        self,
-        sz: impl Into<Option<u32>>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_max_frame_size(self, sz: impl Into<Option<u32>>) -> ClientBuilder {
         self.with_inner(|inner| inner.http2_max_frame_size(sz))
     }
 
@@ -540,10 +515,7 @@ where
     /// Default is currently 16KB, but can change.
     #[cfg(feature = "http2")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http2")))]
-    pub fn http2_max_header_list_size(
-        self,
-        max_header_size_bytes: u32,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn http2_max_header_list_size(self, max_header_size_bytes: u32) -> ClientBuilder {
         self.with_inner(|inner| inner.http2_max_header_list_size(max_header_size_bytes))
     }
 
@@ -551,7 +523,7 @@ where
     /// enabled.
     #[cfg(feature = "http3")]
     #[cfg_attr(docsrs, doc(cfg(feature = "http3")))]
-    pub fn http3_prior_knowledge(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn http3_prior_knowledge(self) -> ClientBuilder {
         self.with_inner(|inner| inner.http3_prior_knowledge())
     }
 
@@ -560,7 +532,7 @@ where
     /// Set whether sockets have `TCP_NODELAY` enabled.
     ///
     /// Default is `true`.
-    pub fn tcp_nodelay(self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tcp_nodelay(self, enabled: bool) -> ClientBuilder {
         self.with_inner(move |inner| inner.tcp_nodelay(enabled))
     }
 
@@ -575,7 +547,7 @@ where
     ///     .local_address(local_addr)
     ///     .build().unwrap();
     /// ```
-    pub fn local_address<T>(self, addr: T) -> ClientBuilder<ConnectorLayers>
+    pub fn local_address<T>(self, addr: T) -> ClientBuilder
     where
         T: Into<Option<IpAddr>>,
     {
@@ -593,14 +565,14 @@ where
     ///     .build().unwrap();
     /// ```
     #[cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux"))]
-    pub fn interface(self, interface: &str) -> ClientBuilder<ConnectorLayers> {
+    pub fn interface(self, interface: &str) -> ClientBuilder {
         self.with_inner(move |inner| inner.interface(interface))
     }
 
     /// Set that all sockets have `SO_KEEPALIVE` set with the supplied duration.
     ///
     /// If `None`, the option will not be set.
-    pub fn tcp_keepalive<D>(self, val: D) -> ClientBuilder<ConnectorLayers>
+    pub fn tcp_keepalive<D>(self, val: D) -> ClientBuilder
     where
         D: Into<Option<Duration>>,
     {
@@ -649,7 +621,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn add_root_certificate(self, cert: Certificate) -> ClientBuilder<ConnectorLayers> {
+    pub fn add_root_certificate(self, cert: Certificate) -> ClientBuilder {
         self.with_inner(move |inner| inner.add_root_certificate(cert))
     }
 
@@ -661,7 +633,7 @@ where
     /// This requires the `rustls-tls(-...)` Cargo feature enabled.
     #[cfg(feature = "__rustls")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls")))]
-    pub fn add_crl(self, crl: CertificateRevocationList) -> ClientBuilder<ConnectorLayers> {
+    pub fn add_crl(self, crl: CertificateRevocationList) -> ClientBuilder {
         self.with_inner(move |inner| inner.add_crl(crl))
     }
 
@@ -676,7 +648,7 @@ where
     pub fn add_crls(
         self,
         crls: impl IntoIterator<Item = CertificateRevocationList>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    ) -> ClientBuilder {
         self.with_inner(move |inner| inner.add_crls(crls))
     }
 
@@ -697,10 +669,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn tls_built_in_root_certs(
-        self,
-        tls_built_in_root_certs: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_built_in_root_certs(self, tls_built_in_root_certs: bool) -> ClientBuilder {
         self.with_inner(move |inner| inner.tls_built_in_root_certs(tls_built_in_root_certs))
     }
 
@@ -709,7 +678,7 @@ where
     /// If the feature is enabled, this value is `true` by default.
     #[cfg(feature = "rustls-tls-webpki-roots-no-provider")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls-webpki-roots-no-provider")))]
-    pub fn tls_built_in_webpki_certs(self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_built_in_webpki_certs(self, enabled: bool) -> ClientBuilder {
         self.with_inner(move |inner| inner.tls_built_in_webpki_certs(enabled))
     }
 
@@ -718,7 +687,7 @@ where
     /// If the feature is enabled, this value is `true` by default.
     #[cfg(feature = "rustls-tls-native-roots-no-provider")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls-native-roots-no-provider")))]
-    pub fn tls_built_in_native_certs(self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_built_in_native_certs(self, enabled: bool) -> ClientBuilder {
         self.with_inner(move |inner| inner.tls_built_in_native_certs(enabled))
     }
 
@@ -730,7 +699,7 @@ where
     /// enabled.
     #[cfg(any(feature = "native-tls", feature = "__rustls"))]
     #[cfg_attr(docsrs, doc(cfg(any(feature = "native-tls", feature = "rustls-tls"))))]
-    pub fn identity(self, identity: Identity) -> ClientBuilder<ConnectorLayers> {
+    pub fn identity(self, identity: Identity) -> ClientBuilder {
         self.with_inner(move |inner| inner.identity(identity))
     }
 
@@ -758,10 +727,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn danger_accept_invalid_hostnames(
-        self,
-        accept_invalid_hostname: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn danger_accept_invalid_hostnames(self, accept_invalid_hostname: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.danger_accept_invalid_hostnames(accept_invalid_hostname))
     }
 
@@ -785,10 +751,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn danger_accept_invalid_certs(
-        self,
-        accept_invalid_certs: bool,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn danger_accept_invalid_certs(self, accept_invalid_certs: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.danger_accept_invalid_certs(accept_invalid_certs))
     }
 
@@ -804,7 +767,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn tls_sni(self, tls_sni: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_sni(self, tls_sni: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.tls_sni(tls_sni))
     }
 
@@ -832,7 +795,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn min_tls_version(self, version: tls::Version) -> ClientBuilder<ConnectorLayers> {
+    pub fn min_tls_version(self, version: tls::Version) -> ClientBuilder {
         self.with_inner(|inner| inner.min_tls_version(version))
     }
 
@@ -860,7 +823,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn max_tls_version(self, version: tls::Version) -> ClientBuilder<ConnectorLayers> {
+    pub fn max_tls_version(self, version: tls::Version) -> ClientBuilder {
         self.with_inner(|inner| inner.max_tls_version(version))
     }
 
@@ -874,7 +837,7 @@ where
     /// This requires the optional `native-tls` feature to be enabled.
     #[cfg(feature = "native-tls")]
     #[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
-    pub fn use_native_tls(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn use_native_tls(self) -> ClientBuilder {
         self.with_inner(move |inner| inner.use_native_tls())
     }
 
@@ -888,7 +851,7 @@ where
     /// This requires the optional `rustls-tls(-...)` feature to be enabled.
     #[cfg(feature = "__rustls")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls")))]
-    pub fn use_rustls_tls(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn use_rustls_tls(self) -> ClientBuilder {
         self.with_inner(move |inner| inner.use_rustls_tls())
     }
 
@@ -907,7 +870,7 @@ where
             feature = "rustls-tls"
         )))
     )]
-    pub fn tls_info(self, tls_info: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn tls_info(self, tls_info: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.tls_info(tls_info))
     }
 
@@ -931,7 +894,7 @@ where
     /// `rustls-tls(-...)` to be enabled.
     #[cfg(any(feature = "native-tls", feature = "__rustls",))]
     #[cfg_attr(docsrs, doc(cfg(any(feature = "native-tls", feature = "rustls-tls"))))]
-    pub fn use_preconfigured_tls(self, tls: impl Any) -> ClientBuilder<ConnectorLayers> {
+    pub fn use_preconfigured_tls(self, tls: impl Any) -> ClientBuilder {
         self.with_inner(move |inner| inner.use_preconfigured_tls(tls))
     }
 
@@ -945,7 +908,7 @@ where
     #[cfg(feature = "hickory-dns")]
     #[cfg_attr(docsrs, doc(cfg(feature = "hickory-dns")))]
     #[deprecated(note = "use `hickory_dns` instead", since = "0.12.0")]
-    pub fn trust_dns(self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn trust_dns(self, enable: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.hickory_dns(enable))
     }
 
@@ -958,7 +921,7 @@ where
     /// This requires the optional `hickory-dns` feature to be enabled
     #[cfg(feature = "hickory-dns")]
     #[cfg_attr(docsrs, doc(cfg(feature = "hickory-dns")))]
-    pub fn hickory_dns(self, enable: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn hickory_dns(self, enable: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.hickory_dns(enable))
     }
 
@@ -968,7 +931,7 @@ where
     /// This can be used to ensure a `Client` doesn't use the hickory-dns async resolver
     /// even if another dependency were to enable the optional `hickory-dns` feature.
     #[deprecated(note = "use `no_hickory_dns` instead", since = "0.12.0")]
-    pub fn no_trust_dns(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_trust_dns(self) -> ClientBuilder {
         self.with_inner(|inner| inner.no_hickory_dns())
     }
 
@@ -977,14 +940,14 @@ where
     /// This method exists even if the optional `hickory-dns` feature is not enabled.
     /// This can be used to ensure a `Client` doesn't use the hickory-dns async resolver
     /// even if another dependency were to enable the optional `hickory-dns` feature.
-    pub fn no_hickory_dns(self) -> ClientBuilder<ConnectorLayers> {
+    pub fn no_hickory_dns(self) -> ClientBuilder {
         self.with_inner(|inner| inner.no_hickory_dns())
     }
 
     /// Restrict the Client to be used with HTTPS only requests.
     ///
     /// Defaults to false.
-    pub fn https_only(self, enabled: bool) -> ClientBuilder<ConnectorLayers> {
+    pub fn https_only(self, enabled: bool) -> ClientBuilder {
         self.with_inner(|inner| inner.https_only(enabled))
     }
 
@@ -992,7 +955,7 @@ where
     ///
     /// Set the port to `0` to use the conventional port for the given scheme (e.g. 80 for http).
     /// Ports in the URL itself will always be used instead of the port in the overridden addr.
-    pub fn resolve(self, domain: &str, addr: SocketAddr) -> ClientBuilder<ConnectorLayers> {
+    pub fn resolve(self, domain: &str, addr: SocketAddr) -> ClientBuilder {
         self.resolve_to_addrs(domain, &[addr])
     }
 
@@ -1000,11 +963,7 @@ where
     ///
     /// Set the port to `0` to use the conventional port for the given scheme (e.g. 80 for http).
     /// Ports in the URL itself will always be used instead of the port in the overridden addr.
-    pub fn resolve_to_addrs(
-        self,
-        domain: &str,
-        addrs: &[SocketAddr],
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn resolve_to_addrs(self, domain: &str, addrs: &[SocketAddr]) -> ClientBuilder {
         self.with_inner(|inner| inner.resolve_to_addrs(domain, addrs))
     }
 
@@ -1013,10 +972,7 @@ where
     /// Pass an `Arc` wrapping a trait object implementing `Resolve`.
     /// Overrides for specific names passed to `resolve` and `resolve_to_addrs` will
     /// still be applied on top of this resolver.
-    pub fn dns_resolver<R: Resolve + 'static>(
-        self,
-        resolver: Arc<R>,
-    ) -> ClientBuilder<ConnectorLayers> {
+    pub fn dns_resolver<R: Resolve + 'static>(self, resolver: Arc<R>) -> ClientBuilder {
         self.with_inner(|inner| inner.dns_resolver(resolver))
     }
 
@@ -1026,50 +982,41 @@ where
     ///
     /// Each subsequent invocation of this function will wrap previous layers.
     ///
-    /// Simple example:
+    /// Example usage:
     /// ```
     /// use std::time::Duration;
     ///
     /// let client = reqwest::blocking::Client::builder()
-    ///                      // resolved to outermost layer, so before the semaphore permit is attempted
-    ///                      .connect_timeout(Duration::from_millis(100))
-    ///                      // underneath the concurrency check, so only after a semaphore permit is acquired
+    ///                      // resolved to outermost layer, meaning while we are waiting on concurrency limit
+    ///                      .connect_timeout(Duration::from_millis(200))
+    ///                      // underneath the concurrency check, so only after concurrency limit lets us through
     ///                      .connector_layer(tower::timeout::TimeoutLayer::new(Duration::from_millis(50)))
     ///                      .connector_layer(tower::limit::concurrency::ConcurrencyLimitLayer::new(2))
     ///                      .build()
     ///                      .unwrap();
     /// ```
-    pub fn connector_layer<S, L>(self, layer: L) -> ClientBuilder<Stack<L, ConnectorLayers>>
+    pub fn connector_layer<L>(self, layer: L) -> ClientBuilder
     where
-        S: Send + Sync + Clone + 'static,
-        L: Layer<ConnectorLayers, Service = S> + Send + Sync + Clone + 'static,
+        L: Layer<BoxedConnectorService> + Clone + Send + Sync + 'static,
+        L::Service: Service<Uri, Response = Conn, Error = BoxError> + Clone + Send + Sync + 'static,
+        <L::Service as Service<Uri>>::Future: Send + 'static,
     {
-        // skipping using `with_inner` here because we need to cast the generic type
-        let inner = self.inner.connector_layer(layer);
-
-        ClientBuilder::<Stack<L, ConnectorLayers>> {
-            inner,
-            timeout: self.timeout,
-        }
+        self.with_inner(|inner| inner.connector_layer(layer))
     }
 
     // private
 
-    fn with_inner<F>(mut self, func: F) -> ClientBuilder<ConnectorLayers>
+    fn with_inner<F>(mut self, func: F) -> ClientBuilder
     where
-        F: FnOnce(
-            async_impl::ClientBuilder<ConnectorLayers>,
-        ) -> async_impl::ClientBuilder<ConnectorLayers>,
+        F: FnOnce(async_impl::ClientBuilder) -> async_impl::ClientBuilder,
     {
         self.inner = func(self.inner);
         self
     }
 }
 
-impl<ConnectorLayers> From<async_impl::ClientBuilder<ConnectorLayers>>
-    for ClientBuilder<ConnectorLayers>
-{
-    fn from(builder: async_impl::ClientBuilder<ConnectorLayers>) -> Self {
+impl From<async_impl::ClientBuilder> for ClientBuilder {
+    fn from(builder: async_impl::ClientBuilder) -> Self {
         Self {
             inner: builder,
             timeout: Timeout::default(),
@@ -1103,7 +1050,7 @@ impl Client {
     /// Creates a `ClientBuilder` to configure a `Client`.
     ///
     /// This is the same as `ClientBuilder::new()`.
-    pub fn builder() -> ClientBuilder<tower::layer::util::Identity> {
+    pub fn builder() -> ClientBuilder {
         ClientBuilder::new()
     }
 
@@ -1201,7 +1148,7 @@ impl fmt::Debug for Client {
     }
 }
 
-impl<ConnectorLayers> fmt::Debug for ClientBuilder<ConnectorLayers> {
+impl fmt::Debug for ClientBuilder {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.inner.fmt(f)
     }
@@ -1238,14 +1185,7 @@ impl Drop for InnerClientHandle {
 }
 
 impl ClientHandle {
-    fn new<ConnectorLayers>(builder: ClientBuilder<ConnectorLayers>) -> crate::Result<ClientHandle>
-    where
-        ConnectorLayers: Layer<ConnectorService> + Send + Sync + 'static,
-        ConnectorLayers::Service:
-            Service<Uri, Response = Conn, Error = BoxError> + Clone + Send + Sync + 'static,
-        <<ConnectorLayers as Layer<ConnectorService>>::Service as Service<Uri>>::Future:
-            Send + 'static,
-    {
+    fn new(builder: ClientBuilder) -> crate::Result<ClientHandle> {
         let timeout = builder.timeout;
         let builder = builder.inner;
         let (tx, rx) = mpsc::unbounded_channel::<(async_impl::Request, OneshotResponse)>();
diff --git a/src/connect.rs b/src/connect.rs
index e1fc599b1..c7898acb9 100644
--- a/src/connect.rs
+++ b/src/connect.rs
@@ -8,7 +8,8 @@ use hyper_util::client::legacy::connect::{Connected, Connection};
 use hyper_util::rt::TokioIo;
 #[cfg(feature = "default-tls")]
 use native_tls_crate::{TlsConnector, TlsConnectorBuilder};
-use tower::{timeout::TimeoutLayer, util::BoxCloneSyncService, Layer, ServiceBuilder};
+use tower::util::BoxCloneSyncServiceLayer;
+use tower::{timeout::TimeoutLayer, util::BoxCloneSyncService, ServiceBuilder};
 use tower_service::Service;
 
 use pin_project_lite::pin_project;
@@ -59,14 +60,10 @@ impl Service<Uri> for Connector {
     }
 }
 
-pub(crate) struct ConnectorLayerBuilder<ConnectorLayers> {
-    pub(crate) builder: ServiceBuilder<ConnectorLayers>,
-    // It's not trivial to identify whether the builder stack is `Stack<Identity, Identity>` or not
-    // so we simply add a boolean flag to track.
-    //
-    // Knowing allows us reduce indirection in certain cases.
-    pub(crate) has_custom_layers: bool,
-}
+pub(crate) type BoxedConnectorService = BoxCloneSyncService<Uri, Conn, BoxError>;
+
+pub(crate) type BoxedConnectorLayer =
+    BoxCloneSyncServiceLayer<BoxedConnectorService, Uri, Conn, BoxError>;
 
 pub(crate) struct ConnectorBuilder {
     inner: Inner,
@@ -82,17 +79,8 @@ pub(crate) struct ConnectorBuilder {
 }
 
 impl ConnectorBuilder {
-    pub(crate) fn build<ConnectorLayers>(
-        self,
-        layer: ConnectorLayerBuilder<ConnectorLayers>,
-    ) -> Connector
-    where
-        ConnectorLayers: Layer<ConnectorService>,
-        ConnectorLayers::Service:
-            Service<Uri, Response = Conn, Error = BoxError> + Clone + Send + Sync + 'static,
-        <<ConnectorLayers as Layer<ConnectorService>>::Service as Service<Uri>>::Future:
-            Send + 'static,
-    {
+    pub(crate) fn build(self, layers: Vec<BoxedConnectorLayer>) -> Connector
+where {
         // construct the inner tower service
         let mut base_service = ConnectorService {
             inner: self.inner,
@@ -107,38 +95,48 @@ impl ConnectorBuilder {
             simple_timeout: None,
         };
 
-        // no user-provider layers so we can throw away our generic input layer stack
-        // and compose with named layers only
-        if !layer.has_custom_layers {
-            // if we know we have no other layers, we can embed the timeout directly inside
-            // our base service call which saves us a Box::pin
+        if layers.is_empty() {
+            // we have no user-provided layers, only use concrete types
             base_service.simple_timeout = self.timeout;
             return Connector::Simple(base_service);
         }
 
-        // we have user-provided generic layer stack
-        let service = layer.builder.service(base_service);
-
-        if let Some(timeout) = self.timeout {
-            // add in named timeout layer on the outside of the stack
-            let service = ServiceBuilder::new()
-                .layer(TimeoutLayer::new(timeout))
-                .service(service);
-            let service = ServiceBuilder::new()
-                .map_err(|error: BoxError| cast_to_internal_error(error))
-                .service(service);
-            let service = BoxCloneSyncService::new(service);
-            return Connector::WithLayers(service);
+        // otherwise we have user provided layers
+        // so we need type erasure all the way through
+
+        let mut service = BoxCloneSyncService::new(base_service);
+
+        for layer in layers {
+            service = ServiceBuilder::new().layer(layer).service(service);
         }
 
-        // no named timeout layer but we still map errors since
-        // we might have user-provided timeout layer
-        let service = ServiceBuilder::new().service(service);
-        let service = ServiceBuilder::new()
-            .map_err(|error: BoxError| cast_to_internal_error(error))
-            .service(service);
-        let service = BoxCloneSyncService::new(service);
-        return Connector::WithLayers(service);
+        // now we handle the concrete stuff - any `connect_timeout`,
+        // plus a final map_err layer we can use to cast default tower layer
+        // errors to internal errors
+        match self.timeout {
+            Some(timeout) => {
+                let service = ServiceBuilder::new()
+                    .layer(TimeoutLayer::new(timeout))
+                    .service(service);
+                let service = ServiceBuilder::new()
+                    .map_err(|error: BoxError| cast_to_internal_error(error))
+                    .service(service);
+                let service = BoxCloneSyncService::new(service);
+
+                Connector::WithLayers(service)
+            }
+            None => {
+                // no timeout, but still map err
+                // no named timeout layer but we still map errors since
+                // we might have user-provided timeout layer
+                let service = ServiceBuilder::new().service(service);
+                let service = ServiceBuilder::new()
+                    .map_err(|error: BoxError| cast_to_internal_error(error))
+                    .service(service);
+                let service = BoxCloneSyncService::new(service);
+                Connector::WithLayers(service)
+            }
+        }
     }
 
     #[cfg(not(feature = "__tls"))]
@@ -298,14 +296,9 @@ impl ConnectorBuilder {
     }
 }
 
-// Struct is public because we can't have private trait in public bounds
-// until we are on MSRV 1.74 when private-in-public was switched
-// from error to lint - https://github.com/rust-lang/rfcs/pull/2145
-// but no internal details are exposed. We don't expose debug
-// for similar reasons.
 #[allow(missing_debug_implementations)]
 #[derive(Clone)]
-pub struct ConnectorService {
+pub(crate) struct ConnectorService {
     inner: Inner,
     proxies: Arc<Vec<Proxy>>,
     verbose: verbose::Wrapper,
@@ -757,16 +750,16 @@ impl<T: AsyncConn> AsyncConnWithInfo for T {}
 type BoxConn = Box<dyn AsyncConnWithInfo>;
 
 pin_project! {
-    // Struct is public because we can't have private trait in public bounds
-    // until we are on MSRV 1.74 when private-in-public was switched
-    // from error to lint - https://github.com/rust-lang/rfcs/pull/2145
-    // but no internal details are exposed. We don't expose debug
-    // for similar reasons.
-
     /// Note: the `is_proxy` member means *is plain text HTTP proxy*.
     /// This tells hyper whether the URI should be written in
     /// * origin-form (`GET /just/a/path HTTP/1.1`), when `is_proxy == false`, or
     /// * absolute-form (`GET http://foo.bar/and/a/path HTTP/1.1`), otherwise.
+
+    // Currently Conn is public but has no implementation details exposed.
+    // We need this because we support pre-1.74 rust versions where `private-in-public`
+    // is a hard error rather than lint warning.
+    // Eventually we probably will want to expose some elements of the connection stream
+    // for layer handling on the tower backswing.
     #[allow(missing_debug_implementations)]
     pub struct Conn {
         #[pin]