Just a warning about buying from Chinese suppliers - Yawn!. I still do it but I haven't always been successful. BMSBattery told me that the Bafang SWXU was disk compatible, so on their advice I ordered a kit. When it arrived, I found it wasn't disk compatible, so I queried it with BMSBattery. They told me I got what I ordered, so they couldn't help me in any way.
My only option would have been to send it back for a refund, but the high shipping cost meant that I would have lost nearly everything. Luckily, I was able to sell the kit on Ebay, so I didn't lose too much.
I also had a bad experience with EVassemble, who didn't package a couple of motors properly, so they got damaged in transit. Paypal said the same : I would have to send them back for a refund, which would have cost even more than I paid for them. Again I had luck. After a lot of phone calls I managed to get the shipper to accept some responsibility and they sent them back free of charge. EVAssemble made be send all the evidence of damage and get confirmation from DHL so that they could claim on their insurance, but they didn't offer me anything. Eventually I got my money back from Paypal. It was a lot of work: four visits to DHL office; about 2 hours on the phone; another hour or so doing photos and sending e-mails - about 6 hours in total!
Morals of the story:
If you buy enough stuff from China, eventually you'll lose something, but you save enough on the other orders to more than compensate for it. There's always a risk with a single order.
Be very careful with the actual ordering process to make sure you select the right things. All their niceness goes out the window once you have something you don't want.