Patternmaster Crio Plus 20ga Benelli Waterfowl Choke Tube. The Code Black Duck is arguably the world's most versatile tube. Imagine a single tube that will get it done in everything from the Arkansas timber, Eastern Shore Geese, all the way Georgia Dove Field and still hold its own on a Missouri Longbeard. The Code Black Duck's versatility is not only in its patented design, but in its construction. Patternmaster's patented stud ring design shortens the shot string immensely...so when you hit your target, you hit 'em with the entire load at once. Expect a tighter pattern similar to a "Full" when shooting 2 3/4-3in shells. Effective distances vary from load and pellet size...but experienced hands should expect clean kills at distances most would consider lucky. Crafted from American made, Titanium Nitride coated 17-4 aircraft quality stainless-steel and are heat treated to the optimum level for best performance. *For best results, Ballistic Performance, LLC, recommends ammunition velocities below 1550fps. *NOT FOR USE WITH SLUG AMMUNITION