Tiger Rock A2 Muzzle Brake is a 1/2x28 threaded five-port birdcage style brake with a solid bottom. It is machined from 4150 steel and finished in a silver phosphate coating. A steel crush-washer is included. Packaged in protective plastic. Specifications: Manufacturer Tiger Rock; Color Silver; Finish Phosphate; Fabric/Material 4150 Steel; Threads per Inch 1/2x28. Package Contents: Tiger Rock A2 Muzzle Brake, Crush Washer.