Staccato HD P4 9mm, 4" Barrel, Black, X-Series Slide, Night Sights, 18 Round Dual-sided safety and slide stop levers, mirrored thumb index points, and reversible magazine catch mean you can run your pistol in either hand with fully mirrored controls and ergonomics. The HOST optic mounting system utilizes spacer plates to allow a "direct mount" of the DPP, SRO, RMRHD, RMR TYPE 2, and HOLOSUN 507/508 SERIES of optics. All of these "top down" mounted optics will use the actual optic screws to thread into the slide, and the spacer plate will be sandwiched between the slide and the optic. You will need the correct spacer plate to mount your desired optic.