Battle Arms Development Thumper, Compensator, 9MM, Nitride Finish, Black, 1/2x36 Threaded BAD-THUMPER-9MM-BN The Battle arms development THUMPER was designed to reduce as much movement as possible when it comes to the muzzle of the gun. This muzzle device does an exceptional job of not only keeping the muzzle flat but mitigating the muzzle flip as well. If reducing felt recoil is your goal" look no further!