Bismuth is a popular material used in shot shells throughout the industry. This shot performs best when paired with the RRaptor BIZ choke. This choke is a strong addition to the RRaptor Series. These choke tubes are built from years of product development and innovations using the highest advanced technology available. They are made out of 17-4 PH U.S. Stainless Steel. *Over-Shotguns can have a RRaptor choke in only one barrel. The design of the choke does not allow for placement in both barrels.*