The Large Brake Adapter will allow the V3 Chronograph to be used with muzzle brakes up to 7.7" in length and barrel diameters up to 1.6" at the muzzle. This product was designed to compensate for the longer muzzle brakes commonly found on large caliber rifles such as the .338 and .50 BMG. The Large Brake Adapter is a milled 6061 aluminum fixture, that uses the included V3 Rail Adapter to clamp onto your weapon's barrel for easy use with your V3 Chronograph's bayonet. *MagnetoSpeed V3 Chronograph not included