The GB-220 clamp on gas block by Sadlak Industries features a clean design with smooth lines and a rounded front enhancing the look of any varmint rifle. Designed for super match or "bull" barrels with a .936" diameter and typically used on varmint rifles with no front sight. The clamp on design assures maximum surface contact to prevent gas blow-by and also prevents loosening due to barrel expansion and contraction. This 6061-T6 aluminum gas block features an extra thick black hard-coat (180 grit sand blast) matte anodized finish. Includes three USA holo-krome #10 Allen head screws. Available with a high or low Picatinny rail.