This AR-15 Muzzle brake with crush washer fits your M4 carbine and M16 rifle barrels with 1/2"x28 muzzle thread in .223, 5.56mm caliber and comes with steel crush washer. This Muzzle brake helps reduce muzzle flash and felt recoil giving you more control over your weapon during rapid fire. This AR muzzle brake is all steel construction, heat treated with Military style black oxide finish. Length: 2.22 inches. Made in the USA.