A flash hider is a muzzle attachment for a firearm used to quickly disperse the burning gases emitted from the barrel so as to limit the amount of flash seen by the shooter. Not only do they serve a purpose, but they also give your AR a custom look. Recommended torque is 15-20 ft-lbs, the use of a crush washer is also recommended. Fits AR-10 or LR-308 rifles with 5/8"-24 threads. Crush washer is not included.