Ergo Grip Gas Block, Low Profile, Adjustable, .750 Barrel, Black Finish 4822 The .750" Low-Pro Adjustable Gas Block is constructed of 4140 chromoly steel and will fit under Superlite Rail Systems. Adjustments are achieved with the set-screw allowing you to fine tune the amount of gas allowed through the system for load specific use. Accepts standard gas tube roll-pin but does not include one.