The CompTek Type I Compensator/Muzzle Brakes is designed for use with .223/5.56 mm ammunition ONLY and will install on firearms with 1/2-28 barrel threads. DO NOT USE WITH LARGER CALIBER ROUNDS. They feature a two chambered brake with an internal gas expansion chamber and 5 top ports to eliminate muzzle rise. This combination virtually eliminates muzzle rise and felt recoil. This brake is protected by a Melonite QPQ surface treatment and is machined from 4140 steel. Product is shipped with installation instructions and an Armageddon crush washer with matching finish to correctly position the device.