Wilson Combat's Adjustable AR Gas Block replaces a standard AR gas block and allows you to tune your direct impingement rifle's gas system for smoother cycling and enhanced reliability. This adjustable gas block is useful on match rifles, suppressed rifles and rifles chambered in non-standard AR calibers, especially when shooting a variety of factory and custom hand-loaded ammunition. The gas block is made of chromoly steel with a melonite finish to hold up to high round count shooting and attaches to your barrel with dual set screws. It is compatible with all standard USGI pattern AR rifles and DPMS pattern LR-308 .308 AR receivers that take standard length gas tubes. Lo-Profile gas block requires 1.45" internal clearance to fit under rails. The package includes: adjustable gas block, adjustment set screw (installed), straight gas tube (installed, gas tube pin installed, and 12" long Allen wrench to adjust inside handguard. This Adjustable Lo-Profile Gas Block measures .750" and has a mid-length, straight tube.