DoubleStar Picatinny Rail HBAR Gas Block Black .750in. gas block. Uses four set screws at 45 degreee angle to ensure block stays tight during heavy use..750" HBAR Specifications for DoubleStar Picatinny Rail HBAR Gas Block: Manufacturer: DoubleStar Color: Black Fabric/Material: 7075-T6 Aluminum Gas Block Journal Size-Diameter: .750 in Gun Make: AR Platform Gun Model: AR-15 Features of Doublestar Picatinny Rail HBAR Gas Block Picatinny rail gas block 4 angled set screws ensure block stays tight during heavy use Size: .750" HBAR Package Contents: Doublestar Picatinny Rail HBAR Gas Block What firearm models does the manufacturer say DoubleStar Picatinny Rail HBAR Gas Block is compatible with? The manufacturer suggests that DoubleStar Picatinny Rail HBAR Gas Block is compatible with AR-15DoubleStar AR453: Picatinny Rail HBAR Gas Block Black .750in