Invector Plus choke tubes are designed for optimum performance with Browning's back-bored barrels. The longer choke taper inside an Invector Plus choke tube, combined with back-boring, produces patterns with uniform densities. Notes: Designed to deliver extremely dense patterns of #4, #5 and #6 turkey loads. Browning has changed finish from Black Oxide to Stainless SteelFor use in Browning back-bored Invector Plus barrels ONLY. Do not use in Invector barrelsCannot be used in both barrels of Browning Cynergy/Citori over/under shotguns.