Armaspec Gas Tube, Mid Length, Fits AR-15/10, Silver ARM653-ML The gas tube plays a vital role in your AR-15 firearm" responsible for directing gases generated in the barrel back into the upper receiver through the gas block and gas tube assembly. Whether you're experiencing issues with your AR-15's performance or seeking a top-quality replacement part" consider Armaspec's selection of gas tubes" crafted from stainless steel for reliable operation.