LOW PROFILE GAS BLOCK FOR AR-15 Steel low profile gas block with .750 Inner Diameter, perfect for any upper build. Includes knurled set screws (2) and gas tube roll pin (1). Machined from 4140 steel with manganese phosphate finish for extended durability. Specifications: 750 low profile gas block Gas blocks are machined in house from 4140 steel finished with a blasted manganese phosphate finish. Knurled set screws included Gas tube roll pin included 425 set screw spacing Mfg: Kak Industry Llc.