Here is a configured beam model in a treatment planning software (Eclipse, Varian) of an electron ultra-high dose rate (>40GY/s) FLASH irradiator from a modified linear accelerator (Varian CLINAC 2100 C/D) utilizing clinical accessories and geometry. The modifications are described in doi:10.1016/j.ijrobp.2021.01.011. The GAMOS produced and confirmed model is included in the file "GAMOS_Beam_Model_100cmSSD". The GAMOS MC simulations for a mouse brain treatment and delivery in a water phantom for validation are included in "GAMOS_Mouse_Treatment_Example". "Run_Code.txt" provides the few lines of code input to terminal to run the simulation with the brain treatment as an example. The GAMOS simulation to produce Eclipse and the Eclipse input files for the beam model are included in the file "Eclipse".