I used this blank to carve a new nut for a cheap violin with a bad nut. I am not an expert luthier, just hobbyist, but I did read some books on violin craft and am happy with my result.
Ebony seems to be a great wood to work with given a decent set of tools. For hobbyists: be aware that this kind of blank will need lots of carving down to size, much more than just minor sanding and setting the string slots. Best read up in a book or two about violin building before carving a nut from a raw piece, or else the result will almost certainly be bad. There are many things to be aware of, or else it will be ruined. The weakest link here is more potentially the craftsman doing the violin setup than the block itself.
I think this product is just fine for use on most violins up into the middle price range.