Carlson's New Bismuth Bone Buster choke tubes are designed to produce excellent, dense patterns with all Bismuth ammunition. 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! Available in Mid Range (.025 constriction) and Extended Range (.035 constriction). The Bismuth chokes can be used with all lead and Hevi-Shot loads. The Mid Range choke tube can be used will all steel shot while Extended Range choke tube can be used with all steel shot not larger than #2. Experience the Bone Crushing dense patterns with these NEW Bismuth Choke Tubes. These chokes come with Carlson’s Lifetime Warranty!