Alan, no barrel specified but, the 9MM ROUGHNECK MODEL is compatible with all standard Bond Arms barrels chambered for 9mm, 357/38 or 45ACP.

Alan, ALL Bond Arms Barrels Fit ALL Models of Bond Arms Derringers*!
100% Interchangeable!
*Barrel Limitations: According to state laws we cannot ship barrels to Massachusetts. In the following areas we cannot ship barrels directly to your house, You must order through a dealer: New York, New Jersey, Washington DC, Chicago. Customers in Maryland are restricted to certain barrels for certain Bond Arms Models, we will ship barrels to your house, but you are responsible for following the laws (click here for Maryland guidelines on which barrels you can purchase).