Extra-length tube lengthens the gas pressure curve to help prevent bolt bounce, short-stroke and feeding jams. Helps prevent cycling problems common to carbines and pistols. Slows bolt carrier to improve feeding reliability and reduce wear and battering. Gives softer recoil impulse, decreases cyclic rate in full-auto fire. Fits under free float tubes and handguards. Carbine fits all 10 inch to 16 inch barrels.