CMC Triggers AR-15/10 Adjustable Low-Profile Gas Block .750 Black Small. This one has a .750 inner diameter the most common size and a low profile that fits under free-float handguards. A front screw adjusts gas flow and a side set screw locks your setting so it doesn't drift. Manganese phosphate finish. Hardware is included: two set screws a roll pin and both adjustment screws. Specifications for CMC Triggers AR-15/10 Adjustable Low-Profile Gas Block: Manufacturer: CMC Triggers Color: Black Fabric/Material: Steel Gas Block Journal Size-Diameter: .750 in Gun Make: AR Platform Gun Model: AR-10 AR-15 Gas Block Journal Size-Length: 0.75 in Handle Color: Black Package Contents: CMC Triggers Adjustable Gas Block Low Profile Fits AR-15 .750 Black What firearm models does the manufacturer say CMC Triggers AR-15/10 Adjustable Low-Profile Gas Block is compatible with? The manufacturer says that CMC Triggers AR-15/10 Adjustable Low-Profile Gas Block is compatible with AR-15 AR-10CMC Triggers CMCGBADJ750: AR-15/10 Adjustable Low-Profile Gas Block .750 Black Small