The Bismuth Bone Buster choke tube is designed to produce excellent dense patterns with all Bismuth ammunition. It is CNC precision machining from 17-4 heat treated stainless steel featuring a longer parallel section (inside the choke) over conventional factory choke tubes. Combine this with extensive testing with various loads and you have the perfect choke to deliver devastating patterns with Bismuth. The Bismuth chokes can be used with all lead and Hevi-Shot loads. Experience the Bone Crushing dense patterns with the Bismuth Choke Tubes. The Extended Range choke tube can be used with all steel shot not larger than #2.