Mount an a red dot sight you to your pistol without having to scratching the slide! On Glock, M&P, and CZ models, the mount replaces the rear sight, turning a standard sight dovetail into an optic mount. On the Ruger Mk series models, the mount replaces the Picatinny rail on the slide, allowing you to mount the optic lower without the use of a Picatinny adapter.