These barrels work well on both Bb and A clarinets. Many musicians are able to use the same barrel on both instruments, with or without tuning rings - an extra perk for the orchestral musician.
Generally, choose the same length barrel that you are currently using on your set-up. If you are very sharp and tend to pull the barrel out more than a millimeter, consider a longer barrel or purchasing tuning rings.
Barrels fit most brands of clarinets with standard tenon diameters. There are exceptions for instruments with non-standard tenon diameters, such as the Selmer Signature. Please feel free to send us an email if you are unsure about the compatibility of your clarinet.