Bowden Tactical Muzzle Brake Black Nitride 4140 Steel with 1/2"-28 tpi Threads 1" Diameter for 5.56x45mm NATO American sourced pre-heated 4140 Steel or Stainless Steel with a brushed finish. Black Nitride coating. Designed to redirect blast and gasses out and up as to mitigate recoil and muzzle rise. They also serve to suppress flash at the end of the barrel. Thread patterns are: 1/2 x 28 with a bore of .280. Designed for .223/5.56 platform. Crush washer included.