I bought a 250w tongsheng and done about 1000km then I had lots of play on chainwheel so I got a new sprag clutch under warranty. I put in on but its so hard to pedal even on highest assist and when I do give it lots of pedal power it slips really bad. Also still had lots of play in chainwheel. This is my second tongsheng that this has happend to, bloody sick of it now. Fit for the bin these units are.