This Yankee Hill Machine Phantom QD flash hider is designed to replace the standard M14 flash hider and sight assembly. Simply remove your stock flash hider / sight assembly, reinstall your stock sight post onto this mount, and install the new assembly onto the barrel. Used in conjunction with the Yankee Hill Resonator and Phantom .30 Cal. Q.D. Sound Suppressors. It retains the excellent flash hiding capabilities of the original Phantom. (Sight base does not fit models with 18.5" or shorter barrels). FeaturesThread Pitch: .595" (19/32)Length: 3 inchesWeight: 5.536 Oz