Q Adjustable Gas Block .750. One screw to increase or restrict the flow of gas to the system and another to lock the adjustment screw in place. We've added a single set screw to the bottom to hold it in place on your 0.75 inch diameter barrel. Specifications for Q Adjustable Gas Block: Manufacturer: Q Color: Silver Fabric/Material: Steel Gas Block Journal Size-Length: 0.75 in Package Contents: Q Adjustable Gas Block The Q GBADJ Gas Block Adjustable .750 is a quality addition to the Q lineup. For more great deals on AR Gas Blocks by Q please browse our Q Gun Parts page. Q GB-ADJ: Adjustable Gas Block .750