These are absolute JUNK!!! Don't buy them!! Since buying these I've had 11 guitars come in for a nut and I've only managed to use 2 of these they don't fit any common guitar, and the ones they do they are too low or the string spacing is wrong, save your money and get them somewhere else. I've been working on Taylor, Martin, Fender, Gibson and others and I've not found these fit anything or are even remotely close.
I would recommend that StewMac redesign these. I was not very pleased with the nuts. They are advertised as white but they are actually a cream color, and the string notches on the Gibson style nuts are extremely deep. Also, the nut is "hollow". If you take a look underneath there is no material, so if you were to fit the nut by shaving the sides there would be a hole going through the nut. It's a good quality, high density plastic, it sounds great, but I think StewMac has to think a little more about these...
Sting notches are too deep, so useless. I tried to use them in my repair shop several times now, and never have been able to. So i still customize my own one. Will never buy that kit again, maybe blank nuts without notches.