Wilson Combat Accu-Tac Flash Hider 5.56 NATO. 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; 11/16" - 24 TPI Length; 1.990" Diameter; .865" Weight; 1.8 oz. Finish; Black Matte Melonite Caliber; .458 Caliber ( .458 SOCOM ) Bore Diameter; .520"; Note: Is not compatable with Rock River Arms .458 SOCOM barrel.; Specifications for Wilson Combat Accu-Tac Flash Hider: Manufacturer: Wilson Combat Fabric/Material: 4140 Steel Condition: New Package Contents: Wilson Combat Accu-Tac Flash Hider Wilson Combat TR-ATFH: Accu-Tac Flash Hider 5.56 NATO