EJ17s offer heavier tension resulting in a bolder, more resonant acoustic tone with higher resistance for heavy strumming and flat-picking. The convenient D’Addario Frustration-Free packaging is fully recyclable and can ship safely in its own box, eliminating unnecessary cardboard boxes and packaging. Buy 10 sets and save with D’Addario Frustration-Free packaging!Phosphor Bronze was introduced to string making by D’Addario in 1974 and has become synonymous with warm, bright, and well balanced acoustic tone. D’Addario Phosphor Bronze strings are precision wound with corrosion resistant phosphor bronze onto a carefully drawn, hexagonally shaped, high carbon steel core. The result is long lasting, bright sounding tone with excellent intonation.D’Addario, the world’s largest manufacturer of musical instrument strings, is known as The Players Choice with a reputation for unsurpassed quality and consistency. D’Addario’s innovative packaging reduces waste and provides protection from corrosion. All D’Addario strings are manufactured in the U.S.A. using proprietary, digitally controlled, state-of-the-art machinery for unmatched performance, set after set.