Three expansion chambers provide up to 45% measured reduction in felt recoil. Triple baffle, exhaust slots redirect noise and muzzle blast away from the shooter. Gives high volume shooters a quiet sounding brake that's easy to clean. Closed bottom keeps exiting gas from blowing up dirt and debris. Tapered shank for easier fitting to different barrel diameters. Adds 1-1/4" to barrel length. Comes with a thread protector. Mfg: Hollands Gunsmithing SPECS: 4340 chrome moly steel. Blue (BL) or 17-4 stainless steel (SS), matte finish. 2" (5cm) long, .850" (22mm) dia. BL A 3/4"-28; 975" (24.7mm) dia, SS A 3/4"-28; 9.80 (24.8mm) dia. Hardened to Rc 42. .250 dia. exit hole, must be drilled out for calibers above .22