The AR10/LR Crush Washer fits most barrel profiles and allows proper attachment of muzzle device and has 12 Pieces per pack. It ensures proper indexing of a flash hider or muzzle brake. AR-10/308 caliber crush washer insures proper indexing of muzzle brakes and flash hiders. Features: No gunsmithing required Thread flash hider/muzzle brake and torque 15 to 20 lb Ensures proper indexing of flash hider/muzzle brake