D'Addario EFT17 Flat Tops Phosphor Bronze Acoustic Guitar Strings, 13-56 D'Addario's popular extra-light gauging with an exclusive precision polishing process for reduced finger noise Smooth, flattened playing surface, superb tone and sustain associated with phosphor bronze strings Corrosion resistant packaging for strings that are always fresh Made in the U.S.A. for the highest quality and performance String Gauges: Plain Steel .013, .017, Phosphor Bronze Wound .026, .035, .045, .056