When finally fitted it works well, however due to the crank arm /chain ring configuration, one bike needs the 'pick-up' round the crank set correcting at the beginning of every ride. It can also be knocked out of alignment during a ride. The installation on another bike required the threaded bar (hub) supplied in the front wheel to be filed down from 10mm to 9mm and that is what we were advised to do to make it fit the front drop out. It was rather precise exercise which some people may not want to tackle. Before purchase check your bike for the existing front drop out size, look carefully at fitting instruction and your crank set up to minimise the fitting problems. So a couple of days to resolve our technical hitches - support was available - then we able to cover 30k reasonably before the batteries ran down. Buy a spare if you can to get a good days ride. (i've not found that ability yet)