Our Accu-Tac AR flash hider sports a three-pronged external profile and our exclusive external accurizing flutes that improve muzzle harmonics over other blast dispersing brakes. These extensively tested features effectively dissipate flash and minimize muzzle signature but unlike many competitive AR muzzle devices, the Accu-Tac has no negative impact on accuracy. Hardened 4140 steel, fits standard, GI threaded AR barrels.Specifications: Material: Hardened 4140 Thread: 1/2" - 28 TPI Length: 1.990" Diameter: .865" Weight: 2.4 oz. Finish: Black Matte Melonite Caliber: 5.56x45mm / .223 Remington Bore Diameter: .360"