The X-Caliber Adapter Set can shoot up to twelve different calibers. This adapter set is a multi-caliber, multi-cartridge barrel insert system that allows shooting the most popular centerfire pistol cartridges through any break-open action 12ga. or 20ga. shotgun. Each insert is essentially a premium quality pistol barrel machined from steel and contoured to fit into the shotgun chamber. Once inserted, the cartridge for that insert can be chambered and fired in the shotgun in the same manner as the shotshell. X-Caliber inserts can be installed and removed without tools or any modification to the shotgun. Inserts for 20ga. shotguns include 9mm luger, .38spl/.357mag, .45acp and 410ga/45Colt. Inserts are sold as a complete set or can be purchased separately. The X-Caliber inserts add unparalleled versatility to a 20ga. break-open shotgun.