Patent Pending Anti-Fouling Design: The adjustment screw never contacts gas port carbon, so it remains clean and operational without risk of seizing; Precision Adjustability: Control your gas flow to optimize your AR15's performance under any shooting condition, with 14 tactile settings from fully open to fully closed; .625" Gas journal compatibility; 3 set screw mounting for added security; Adjustment screw can be turned with either a 3/32" allen key or a flat head screwdriver; 1" in length