Timber Creek Outdoor Inc Heart Breaker Muzzle Brake 223 Rem 1/2"-28 tpi Black Cerakote Aluminum Timber Creek's Heart Breaker Muzzle Brake Is Compatible With Barrels having a Bore Diameter Of .223 Or Less And 1/2-28 Muzzle Threads. Includes Locking Nut. Model: Heart Breaker Material: Aluminum Thread Pattern: 1/2"-28 tpi Finish: Black Cerakote