The Grey Ghost Precision Glock Version 1 Pistol Slide w/ RMR-DP Pro Cut includes shim plates used for when you want to install either a RMR style optic, or DeltaPoint Pro (DPP) style optic. Since the optic cut is designed for two different footprints, you must use the correct shim (included) to install an RMR. It also includes a G10 cover plate and proper screws for cover plate, and correct length screws for RMR and DPP.