Luth-AR Adjustable Gas Block AR-15/ M16 5.56x45mm NATO/ .223 .750in Inner Diameter 4140 Chrome Moly Vanadium Nitride Black. Specifications for Luth-AR AR-15 Adjustable Gas Block .750 ID: Manufacturer: Luth-AR Color: Black Fabric/Material: 4140 Chrome Moly Steel Gas Block Journal Size-Diameter: .750 in Caliber: 5.56x45mm NATO .223 Remington Gun Make: AR Platform Gun Model: M16 AR-15 Weight: 1.6 oz Condition: New Length: 1.04 in Width: 0.94 in Finish: Nitride Height: 1.33 in Features of Luth-AR AR-15 Adjustable Gas Block .750 ID 4-40 x 3/16? Gas adjustment screw set screw (secures the gas adjustment screw once set) Double Inspected and highest quality Individually bagged Package Contents: Luth-AR AR-15 Adjustable Gas Block .750 ID What firearm models does the manufacturer say Luth-AR AR-15 Adjustable Gas Block .750 ID is compatible with? The manufacturer suggests that Luth-AR AR-15 Adjustable Gas Block .750 ID is compatible with AR-15 M16Luth-AR GB-750-A: Adjustable Gas Block AR-15/ M16 5.56x45mm NATO/ .223 .750in Inner Diameter 4140 Chrome Moly Vanadium Nitride Black