Maybe I'm too fussy, but I'm a cabinet maker, so I work with sharp edges; I count it as sharp if I can shave the hairs on my forearm with it. This device got the first few knives just about that sharp, but the tiny area of diamond actually doing the work means that it wears very fast, and it was very soon a lot less effective. If your knives are quite blunt, you'll quickly wear this out sharpening them; if they're quite sharp, it won't put a real razor edge on them; if they're somewhere in between, it'll improve them a bit.