The Winchester Super X4 is built for the marsh with tough conditions in mind. The SX4 is based on the bullet proof Active Valve gas operating system that was the core foundation of both the SX3 and SX2. The Active Valve has been tested tried and tweaked to perfection to make it the most trusted autoloader in the marsh. Includes three Invector choke tubes full modified and improved cylinder and sling swivel studs. SX4 WATERFOWL 20/28 RTL 3" #