Invector-Plus choke system. The proven Invector-Plus interchangeable choke tube system works hand-in-hand with back-boring to offer consistent dense shot patterns with just the constriction needed for the shooting situation. The longer choke taper inside an Invector-Plus choke tube produces consistent patterns with more uniform densities and fewer fliers. The superior design of the Invector-Plus system is far more durable than the choke systems found in our competitors guns especially when shooting steel shot. Invector-Plus eliminates gases slipping between the choke tube and barrel that could damage the choke tube and the barrel. – Find the performance you need. Winchester Repeating Arms shotguns with Invector-Plus are supplied with a variety of choke selections and configurations depending on the model. Most Winchester’s with Invector-Plus feature flush mounted versions in various finishes. Extended tubes are standard on some models and are also available as accessory items from Browning. Check out the list of tubes below by clicking on the black bar to reveal availabe options. They include the full range for open to tight as well as special turkey tubes.