This genuine, Colt factory part is the one used by our GI’s on the M-4 carbine to allow attachment of M203 grenade launchers or forward mounted lights and lasers. Steel, two-piece unit clamps directly around the barrel between the barrel bands of the Mil-Spec front sight housing. Can be mounted at the right or left side of weapon and features a rubber-coated swivel to eliminate sling abrasion and noise.  No modifications or gunsmithing required. Also fits AR-15/M16 rifles with conventional front sight housing. SPECS: Black, hardened steel. 9?16' (1.4cm) long, 1-11?16'(4.3cm) wide. Fits barrels .650' (16.5mm) to .750' (19.1mm) diameter.