Carlson's Delta Waterfowl Choke Tubes are manufactured from 17-4 heat-treated stainless steel and designed to throw tighter and denser patterns than conventional choke tubes. These choke tubes feature a 25 percent longer parallel section in the choke, thus throwing more consistent patterns. Each choke tube is knurled on the end to allow for quick and easy removal and has the constriction and type laser marked on the end and body for easy reference. free case included comes with Close, Mid, and Long Range chokes will Extend 1" out of barrel Cannot use steel shot larger than #2 or faster than 1550 FPS through the Long Range choke