Battle Arms Development, Thumper, Compensator, 9MM, Nitride Finish, Black, 1/2x36 Threaded WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov. 17-4 Stainless Steel 9MM, 1/2x36 Threaded, 2.5oz Does not include a crush washer Black Nitrite Finish 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!