Guntec USA AR-15 Crush Washer 1/2-28 Stainless

A crush washer is what lets a muzzle device end up pointed the right way. Thread the device on, torque it down against the washer, and the washer deforms until the ports or tines sit where they belong, then keeps them there through recoil instead of letting the device walk loose.

This one is stainless rather than plain steel, so it shrugs off the heat and weather that work on a muzzle. Sized for 1/2-28 threads, the standard on AR-15 barrels in 223 Rem and 5.56, and it fits under any flash hider, brake or compensator cut for that thread pitch.