Both Standard Invector? and Invector-Plus? tubes are available in constrictions ranging from Cylinder to Extra-Full. Longer choke taper inside Invector-Plus choke tubes. Produces patterns with excellent uniform densities. All Browning tubes are set to industry constriction standards. Excellent patterning. Constructed of highly polished, 17-4 stainless steel for the ultimate in performance and durability.