These are the finest nylon folk, ball end guitar strings offered by D'Addario. These have 80/20 bronze wound basses with multi-filament cores with clear nylon trebles. The trebles are gauged .028, .032, and .040, and the basses are .031, .037, and .045. These will work on a variety of classical or steel string acoustic instruments. You will have great sound with these strings. These are new and in the original packing with the strings sealed in their exclusive Corrosion Intercept Bag.