DYE Precision GF Boomstick Barrel Steady Port Pressure Porting: Trademark muzzle port design is a key feature that gives DYE barrels unparalleled accuracy and a low sound signature Stainless Steel Insert: At the heard of the CF and GF Boomstick is a gun drilled, surgical grade, 303 stainless steel insert. This gives you the smoothest and straightest surface finish. 303 stainless steel is extremely high quality material that is both corrosion and scratch resistant Two-Piece Construction: DYE's innovative CF and GF Structural Wrap construction has set a new standard for lightweight performance GF Barrels are produced in Cocker/Matrix marker threads Available in 15". Bore sizes 0.684 and 0.688