All I can say is DON'T.
I have had the "pleasure" to compare an ebay file to a proffessional one. And the difference is HUGE.
The ebay one was shaking, therefor breaking down the acrylic nail, it felt so bad when filing, not only for the hand holding it, but for the nail being filed as well.
It was noisy etc. and if it was to breake how would you get it repaired?
I would by an e-file with a trusted company who offers training aswell, as this is a tool that in the wrong hands can do so much damage.
ps. this ebay file looked like the pro one, you couldn't see the difference, bot boy did you feel it!