This is a Stokemonkey motor and controller for tandems or other large bikes. It comes with a special left hand crank and chain ring which is driven by the motor, and also an aluminum clamping block which attaches it to your bike frame. It was lightly used when I got it - I tested it and it worked fine, but I never ran it on a bike. I now have it set up to run on the bench with a 48 volt battery pack, so I can show it to you running. Please reply with a phone number and some word to let me know you are real bike rider and not just skimming emails. Thanks!