Manufactured from 17-4 stainless steel and hardened. For use with lead shot in all constrictions. Steel shot larger than #BB should not be used in any choke tighter than modified, BB and smaller size steel shot may be used through full choke constriction.Interchangeable with Winchester, Mossberg, Browning Invector, Weatherby, and Savage 12 gauge & 20 gauge shotguns.