Forward Controls Design AR-15 Gas Block .750in Black GBF. Made from heat-treated 4140 bar stock and coated with manganese phosphate the GBF AR-15 gas block maintains tight tolerances for effective sealing. Featuring a semi-blind gas tube hole design the GBF includes bosses on both sides for easy pinning to the barrel. Features gas tube pin and knurled set screws. Specifications for Forward Controls Design AR-15 Gas Block: Manufacturer: Forward Controls Design Color: Black Fabric/Material: 4140 Steel Gun Make: AR Platform Gun Model: AR-15 Finish: Heat Treated Package Contents: Forward Controls Design AR-15 Gas Block Gas tube roll pin Mounting screws What firearm models does the manufacturer say Forward Controls Design AR-15 Gas Block is compatible with? The manufacturer says that Forward Controls Design AR-15 Gas Block is compatible with AR-15Forward Controls Design GBF 0.750: AR-15 Gas Block .750in Black