Smith Enterprise Good Iron AR-10 LR-308 Muzzle Brake. 14-port muzzle brake in 5/8-24 thread. Constructed from 8620 steel and finished with salt bath nitriding for corrosion resistance and durability. Upper ports reduce recoil and muzzle rise; lower portion is closed to reduce dust signature when firing prone. Includes jam nut for timing the brake on your rifle. Matte finish.