I'm using one on this bike, because I didn't want to pay to have anymore quill stems turned down to 21.1mm when I changed bars. So, I had my machine shop turn down this adapter from VO. I tapped it for a bell and gave it a quick polish to blend in with the chrome. The combination of the adapter and threadless stem made the cockpit much stiffer in (for me) a good way. I ride tall frames and mushy front ends are all too common.