Product Information : D’Addario’s heaviest 80/20 Bronze gauge, EJ12s offer heavier tension resulting in a bolder, more resonant acoustic tone with higher resistance for heavy strumming and flat-picking. D’Addario’s heaviest 80/20 bronze set, ideal for heavy strumming and flat-picking Extra-bright tone mixed with deep and projecting bottom end Environmentally friendly, 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, Bronze Wound .026, .035, .045, .056 80/20 Bronze, commonly referred to as brass, is the original acoustic string alloy selected by John D’Addario Sr. and John D’Angelico in the 1930s. 80/20 Bronze strings are popular for recording due to their crisp, deep and projecting tone and appeal to many traditionalists and vintage enthusiasts for their historical significance. All D’Addario acoustic strings are wound on a hexagonally shaped, high carbon steel core, resulting in long lasting, bright sounding tone with excellent intonation.