The product does what it promises well. I use it on metal knives. Of course, it cannot be compared to manual sharpening (if anyone can do it) and it removes a lot of metal from the knife. I would not use it on expensive knives.

The stone is not centered. Out of the 4 notches, only one can be used. Not convenient at all.

I bought it, used it on 2 knives, and it destroyed them. I returned it (very good experience with the return and exchange) as defective and they sent me a better one, but it still doesn't sharpen the knives correctly. I wouldn't trust it with a knife worth more than 30 euros, better to get something else... Obviously, it doesn't sharpen ceramic knives, and it makes the rest of them weird no matter how correctly you sharpen them.