This pigtail gas tube was designed to solve timing problems for over-gassed 7.5 AR pistols. The pigtail design causes the tube to simulate a more standard cycle time and helps remedy timing problems without patchwork like a heavier buffer, etc. This allows the shooter/builder to use standard Mil-Spec carbine parts for better reliability. It fits all barrels using a pistol length gas system with an outer diameter at or below 1.