If your AR-15 pistol with a 7.5 inch barrel has timing issues due to being over-gassed, the Phase 5 Pistol Pigtail Gas Tube is the solution to your problem. The Phase 5 Pistol Pigtail Gas Tube design adds length to an otherwise short gas tube, having the effect of simulating a standard cycle time. The Phase 5 Pistol Pigtail Gas Tube is a quick and inexpensive way to solve your timing problem, because it frequently tames even the most over-gassed AR pistols without the need to experiment with buffer weights, different carriers, etc. A more mil-spec pistol means a more reliable pistol. Loop diameter: 1.46 to 1.56 inches Material: Stainless steel The Phase 5 Pistol P Mfg: Phase 5 Tactical