The thing I didn't like about the Shiftmate was that you were then locked into the other cassette type unless you wanted to change the ratio each time, and I'm not even sure that's possible. What I needed was to be able to use either a Campy wheel or my Shimano Kickr Core trainer with a quick swap. I just take off my wheel and put the bike on the trainer and it is ready to go, and vice versa and I never have to fuss with anything. The two different cassettes are perfectly aligned with each other so no adjustment ever needed. I'm still sometimes amazed I made it work that way.