First off, be aware that these bone blanks need to be degreased, before use. These bone blanks are unbleached, meaning the blank still contains fat, and the fat will seep out if not degreased.
I use either Acetone or rubbing alcohol for the degreasing part - and I find that Acetone does the trick really well.
Using these bone blanks without degreasing them could, over time, cause the fat to seep into the nut channel and the wood - which wouldn't really be all that good...
I would recommend to degrease the blanks and then square the edges up, using sandpaper, to really get the blanks well prepared.
I've bought many of these nut blanks over the last year and a half, and I'm very happy with the results I've gotten out of them.
This particular nut blank is a little thicker than the other option from Göldo, so this one is perfect for fitting on a Les Paul type guitar or any acoustic guitar.
The processing of these bone blanks are excellent, and very accurate, I've never had any problems with them not being square.