I just helped a friend install a Tongsheng 500 mid drive motor on his Schwinn 29er. Easy install, it does not have a throttle, instead its a torque sensing unit with 4 levels of power. So you must pedal it. We got it from Roshan at Biktrix located in Saskatoon, Saskatchewan, Canada. This is the 2nd kit I've got from him, he's been a real pleasure to deal with. Turns out I did not install the speed sensor properly, it needs to be moved over approx 1/2 ". Other than that the job from start to finish took about 3 hours. It is the start of winter here and the sun sets before 5pm but today was just above freezing so once we finished hooking it up , my friend got a few test runs. Very nice unit, seems seamless in the power delivery. He bought it with a 48 volt battery but it's supposed to be able to handle up 60 volts.