The tubes fit flush with the end of the barrel but are longer than competitors' tubes. The Extended tubes are available as accessory and are even longer. The Proprietary differential banded gas seal eliminates residue build up and makes chokes easy to remove and install. Integrated spring suspension holds the seal tight, yet allows expansion against the barrel wall for a perfect fit and a smooth transition for shot column entering choke, Gas is controlled at the interface between choke and where it seats in the bore. From skeet to full choke, patterns tighten consistently and reliably