There is a risk, as with anything, that a cheaper product has not been made to the same standards. There may be nothing wrong with the eBay one, but most people will likely advise you to stick with either a Motordyne or one of Wasso's as the quality of these are tried and tested. I have a Wasso one and there were no fitment problems, the quality is excellent and you can get it anodised in your choice of colour, so they look cool too!