I am using these strings on a medium-range, Spanish factory-made Flamenco guitar...solid spruce top, laminated Sandalwood back and sides. The guitar was setup at the factory with D' Addario Pro-Arte normal tension strings and sound and feel was very good, but I was looking for a little more brightness without brittle sound. Luthier 20 strings give this brighter quality, but with richness for this guitar, and from use of this set on other instruments they last a long time in my experience, as do the D' Addario.
Keep in mind your results may vary, a lot depends on the instrument and your playing style of course, but I am very happy with these strings!
The 3rd/G/sol is a little "tubby" as many Flamenco guitarists will comment on about many strings, but on my guitar it is not so much as other brands.
I like that the basses are vacuum-packed. Trebles are not but all treble strings I have tried seem to not be affected by the same (reasonable) conditions that can affect basses.
Anyway, objectively I think these are very well made strings, and subjectively work very well on my guitar!
