On the curved based rings, you may still have to sand the bottoms down in order to get the same radius curve as the top of the guitar. The ones I've got for my ES-3 have a 1mm gap between ring and body at the moment, as the top is less curved than a Les Paul's. I could have gone for flat ones and sanded the curve in, but they are often not as tall as the curved bottom rings, so the neck one could have been too small to sand the right curve in without making it too thin and weak in the middle. But they are cheap enough to simply get some more if I make a mistake.