Cal. 7.62, Muzzle Thread: 5/8-24 When mounted to a 14.5-inch barrel, overall length extends 16 inches. All Compensators have an outer diameter of 22mm (NATO Spec.). All Compensators come with Crush or Peel-Away Washers. Like all Vltor product, we recommend the installation to be preformed by a qualified gunsmith and/or experienced armorer.