The Invector-Plus tubes are longer choke taper inside and produces patterns with excellent uniform densities. It is set to industry constriction standards and have an excellent patterning. The choke tube is constructed of highly polished 17-4 stainless steel for the ultimate in performance and durability. Invector-Plus choke tubes fit only Browning shotguns designed for Invector-Plus and are NOT for use in shotguns showing Standard Invector or Invector-DS on the barrel(s).