This genuine, USGI part is the one used on the AR-15 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 all AR-15/M16 rifles with conventional front sight housing. Can be used with .625 barrels.