Our standard mainspring housing with a precision machined slot, and a drilled and tapped hole cut into the bottom. This superior two-piece design allows easy, drop-in installation of our included magwell, as well as easy removal of the magwell in seconds, without disassembling the pistol. Greatly increases magazine well opening for flawless magazine changes and speedy reloading. No grip modifications required. Internals not included, may be purchase separately if needed.