Agency Arms Modular Magazine Release Gen 3 Compatible Black. The MMR was designed to give the end user options allowing them to select a magazine release face that suits their needs. Compatible with Gen 3 double stack models. Does not fit single stack wide frames and Gen 4 models. Specifications for Agency Arms Modular Magazine Release: Manufacturer: Agency Arms Color: Black Finish: MIL-A-8625 Type 2 Anodize Fabric/Material: 6061 Aluminum Features of Agency Arms Modular Magazine Release Material - 6061 Aluminum Coating - MIL-A-8625 Type 2 Anodize Color - Black Magazine Faces - 3 Sizes (Small Medium Large) Compatible with Gen 3 models (Will not fit wide frame models) Package Contents: Agency Arms Modular Magazine Release Agency Arms 25MR-G3MM-B: Modular Magazine Release Gen 3 Compatible Black