Take a good look at the pictures of the Ultrafire C8 knockoff in this thread. The one I got had a plastic pill and wasn't completely machined so a standard C2/C8 pill wouldn't fit so it was useless to mod.
I got a C2 kit from DX and built it and protected 18650 do not fit in the DX version so keep that in mind also.
If you pay $11 for that light then $9 for an XML emitter then $5 for a driver that's $25 and you have to put it together and hope you don't mess it up. You can buy the the KD C8 for less money and it is an awesome light no gamble on possibly getting a piece of junk you can't use.
http://www.kaidomain.com/ProductDetails.aspx?ProductID=11278
I really like the C2 kit light I built it handles the heat from an XML at 2.8amps no problem and it has awesome throw with that big reflector, but not being able to use protected batteries stinks.