Combat Hunting is your source for a crush washer for an A2 flash hider muzzle brake for 1/2"x28 Thread AR-15, M4 carbine or rifle barrel on sale. Our steel crush washers for AR 15 muzzle brakes come three to a pack in this kit. The crush washer for your AR-15 muzzle brake flash hider allows you to properly time your muzzle brakes on your AR barrels with 1/2"x28 thread. Crush washer is solid steel construction with a black finish. Outside Diameter: 0.75" Inside Diameter: 0.50"