Diamondhead USA, Inc. Receiver Height Gas Block Gas Block w/ Rail Overhang Black AR-15 556NATO .750" 3101 Model: Receiver Height Gas Block Caliber: 556NATO Finish/Color: Black Fit: AR-15 Size: .750" Type: Gas Block Manufacturer: Diamondhead USA, Inc. Model: Receiver Height Gas Block Mfg Number: 3101