I was looking at a bunch of mid drive motor set ups and I finally decided to try the Bafang BB02. The geared motor, controller, and bottom bracket crank set come as a unit and slide into the bottom bracket. Slide might be an exaggeration. Mine required a little work with a file to enlarge the bracket slightly and I also sanded the paint off the part that fits into the BB to get it to fit. The 'throttle' is basically an on-off switch and there are 3 levels of assist. The speed at each level is: 1. 18kph-11mph, 2. 22kph-13.6mph, 3. 32kph-19.8mph. These speeds meet the federal limit of 20mph and the speed is limited electrically. The motor accelerates very briskly up to the limit and I'm sure if the governor could be bypassed/eliminated the moter is capable of at least 30mph. The earlier Bafang BB01 was a 250 watt unit, primarily designed to meet Europe's very low limit for e-bikes. The newer BB02 is available in 36 and 48 volts and up to 750 watts. The 500 watt unit I got is about 2/3 horse power, and seems very adequate. The only changes I would like to see is a analog throttle and an electrically governed speed limit that could be adjusted higher, to at least 25mph. The quality of the unit/components seems to be of a high level and I am very satisfied. I orderede the unit from tnabattery-ebike in China and paid for it through paypal. the shipping via DHL was about $80.00 US and delivery was timely, if not quick. The only piece missing was the magnet for the speed control/consol. No big deal as I had several from old Catseye speedos and they work fine. Everything was packed well and nothing broke in shipment, though the box was slightly smuched. The Bafang unit is installed on my old e-bike that was powered by an e-bikekit direct drive hubmotor with a dead controller. It has better acceleration and is lighter than the old hub motor.