I bought the mandolin version and fitted it to my Gibson. There's a lot of extra material to remove, but the result was great. Easier tuning (the old nut had tight slots for the A strings), better intonation. Later I used one of the extra frets in the package to fix a tenor guitar. For that, I simply filed the necessary ledges in the existing nut and widened the string slots. It would be nice if Stew-Mac would also sell the offset tang frets separately, for retrofitting to an existing nut.
Just put one of these on an old beater of a cheap strat-clone kit that I use to experiment with "creative" wiring. Suddenly its in tune up and down the neck and stays that way after using the trem as well. It cost half the price of the kit but it has significantly improved the value of the instrument to me. It required a little sanding of the back of the nut but nothing drastic. I dont have many dedicated luthier tools so the fret wire is not trimmed perfectly (but the look is in keeping with the overall "relic'd" appearance of the guitar). The question now becomes can I get a discount if I order these in bulk?
One for Fender Telecaster, the other for Breedlove acoustic. Both of these guitars are top 10 instruments. The Zero Glide nut improvement came through as described on Youtube demos. So much better string action (lower with out any fret buzz) Clarity in open string tone chords and pulloff plucking, faster tuning to pitch, using electronic tuner, remaining in pitch once strings stretch has settled in. I took my time to install on both guitars about 2 hours for each instrument. Have new custom Guitar that I will 99% sure I will add this improvement to soon. I see this becoming a standard upgrade to many popular manufactures. Lastly the sustain in open chords on all strings cant be described.
Great product, Makes a lot of difference in sound and play ability. To say nothing of staying in tune. I put one on a Ovation Legend made in 1972. The guitar always sounded good but was a little tough to play. This made a world of difference. It is now amazing. I have a friend who can't keep his hands off of it. He likes it better than his Rainsong.