Pro-Arte are D'Addario's premium classical guitar string sets and are the world's most popular classical guitar strings. All Pro-Arte treble strings are sorted by a sophisticated computer-controlled laser machine which performs diameter and tension measurements, ensuring true-sounding, precise trebles in every set. The EJ47 normal tension set features 80/20 bronze wound basses providing brighter acoustic tone, comfortable feel and dynamic projection. 80/20 is the original acoustic string alloy selected by John D'Addario Sr. and John D'Angelico back in the 1930s. Like all D'Addario strings, they come in corrosion resistant packaging for consistently fresh strings in every set.