Masterpiece Arms Bolt Action 6.5mm Muzzle Brake 5/8x25 NitrideBlack. Using our special testing system we have tweaked the design to achieve a 63percent reduction in recoil. The jam nut collar system utilizes a design that allows the shooter to jam the nut and brake against each other in the appropriate position on the muzzle of the rifle. There are 2 machined flats that are used to both level the brake body as well as interfacing with an adjustable wrench for installation of the brake. It not only eliminates the need for ground shims but also aligns the ID of the brake perpendicular with the shoulder of the barrel minimizing initial point of impact shift. Specifications for Masterpiece Arms Bolt Action 6.5mm Muzzle Brake: Manufacturer: Masterpiece Arms Color: Black Projectile Caliber: .264 Caliber Finish: Nitride Fabric/Material: Steel Threads per Inch: 5/8x24 Package Contents: Masterpiece Arms Muzzle Brake 6.5mm 5/8x24" Black