This muzzle brake is 4.5" long and a perfect addition for sniping. It is compatible with all 1 inch tip .68 caliber barrels. It is also the best thread-on muzzle brake for the Tactical Series barrel and is nice on the T68. The M177 Whisper Muzzle Brake is also compatible with T68 series barrels, tactical barrels, and tactical rifled barrels. Installation is quick and easy.