Presma 0.750 Low Profile Gas Block for AR 15 .223/5.56 Stainless Steel. 223/5.56 0.750in Diam. Barrels. Includes roll pin screws & hex wrench Specifications for Presma AR-15 0.750 Low Profile Gas Block: Manufacturer: Presma Fabric/Material: Stainless Steel Gas Block Journal Size-Diameter: .750 in Caliber: 5.56x45mm NATO .223 Remington Gun Make: AR Platform Gun Model: AR-15 Package Contents: Presma AR-15 0.750 Low Profile Gas Block Pin Allen wrench What firearm models does the manufacturer say Presma AR-15 0.750 Low Profile Gas Block is compatible with? The manufacturer suggests that Presma AR-15 0.750 Low Profile Gas Block is compatible with AR-15Presma GB04: 0.750 Low Profile Gas Block for AR 15 .223/5.56 Stainless Steel