Gas tubes are integral components of the AR-15 gas system in an AR-style rifle, specifically facilitating the direct impingement operation that drives the firearm's cyclic action. Typically made of stainless steel, these thin, tubular structures channel high-pressure gas from the gas block, located on the barrel near the muzzle, back to the bolt carrier group within the upper receiver. As the projectile passes the gas port on the barrel, a portion of the expanding gases is diverted through the gas block and into the gas tube. This redirected gas forces the bolt carrier group to unlock and cycle, enabling the rifle to eject the spent cartridge and chamber a new round. Gas tubes come in various lengths, including carbine, mid-length, and rifle, to accommodate different barrel lengths and configurations, ensuring proper timing and functionality of the firearm.