Model: GB210 .936 Bore Diameter Low Profile Aircraft Aluminum Clamp Type, #10 Socket Screws Enclosed Gas Tube Hole Bull Barrel Hard-Coat Black Anodize All of SADLAK's Gas Blocks are made in the USA by craftsmen with years of experience delivering consistent quality. All the bores are precision honed and all critical measurements are 100% inspected to insure consistancy and quality. Mfg: Sadlak Industries