http://www.tjbewo.com/En/CMS.aspx?cid=3
For USD 177, it is quite tempting. But can it install into any kind of bike?
http://stepinternational.en.made-in-china.com/product/dvcnMNDUAahi/China-36V-250W-MID-Drive-of-Electric-Cycle.html
IMHO, the Bafang BBS01 is a safer choice....