Whenever this subject comes up, I always say the same thing - "buy cheap, buy twice" before directing the questioner to kipon, novoflex and fotodiox all of which are well made and reliable in my personal experience. I have had bad experiences with cheap "generic" adaptors from eBay sellers; not made to tolerances/ill fitting (I have had ones that bind, and one that rattled and drooped on the body) I have also had ones that have had swarf on the mount - not what I want on my sensor, thank you. Returns have been problematic too - the sellers of these items tend to dissemble and squirm and try to refuse returns and refunds. Caveat emptor and all that, but I'd stick to the well-made items and not run the risk. Ask yourself this - do you really want to stick a ten quid adaptor between your 500 quid camera and 500 quid lens...?