I put these on my New Hartford Guild F30, to see how they would preform. normally 12's are recommend on this size, style guitar, but I felt I wanted to try something slightly beefier, so with these the core is round rather than hexagonal which lowers the tension. I was previously using Martin retro 12's which are very nice and suit the guitar quite well. This thin core GHS set feel lovely under the fingers and a'rent quite as heavy and the standard 13 gauge set, the string set is very balanced from E-E and the volume and clarity has also increased, very pleased with them. Going to try GHS on my telecaster next, hopefully with similar results!!! Thanks