EJ17s offer heavier tension resulting in a bolder, more resonant acoustic tone with higher resistance for heavy strumming and flat-picking. D'Addario's most popular choice for heavy strumming, flat-picking and resonant, projecting tone Preferred for its warm, bright, and well balanced acoustic tone 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, Phosphor Bronze Wound .026, .035, .045, .056