no firearm selected However if you are asking about the Ruger Blackhawk convertible (and most single action revolvers ) then yes it does come with 2 cylinders if you are looking at a double action revolvers some have 2 cylinders and some require the use of Moon clips to use the 45ACP

David, no firearm specified. just let us know the model or item number. Thanks much! Most "Convertibles", "Combi's", and revolvers with / between 2 Calibers in the Title such as 22LR/22Mag will come with the 2nd caliber cylinder.