Extended Invector DS Choke Tubes have the Proprietary deferential banded gas seal that eliminates residue build up and makes chokes easy to remove and install. The Integrated spring suspension holds the seal tight yet allows expansion against the barrel wall for a perfect fit and a smooth transition fro 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. Available only on the Citori 725 and the upcoming Browning A5.