VG6 Precision VG6 Gamma 556SL Muzzle Device for AR-15 Black Nitride Black. The Gamma 556SL is long enough to provide an overall length of 16" when permanently affixed to the barrel. Its outside diameter of .745 inches allows you to install and service your gas system without removing the muzzle brake. The 3-chamber design looks great on any standard profile barrel while effectively eliminating recoil leaving your rifle shooting flat and soft. Specifications for VG6 Precision VG6 Gamma 556SL Muzzle Device: Manufacturer: VG6 Precision Color: Black Finish: Black Nitride Gun Make: AR Platform Gun Model: AR-15 Length: 16 in Condition: New Diameter: 0.745 in Country of Origin: USA Package Contents: VG6 Precision VG6 Gamma 556SL Muzzle Device What firearm models does the manufacturer say VG6 Precision VG6 Gamma 556SL Muzzle Device is compatible with? The manufacturer says that VG6 Precision VG6 Gamma 556SL Muzzle Device is compatible with AR-15VG6 Precision APVG100038A: VG6 Gamma 556SL Muzzle Device for AR-15 Black Nitride Black