Pro-Arte, the world's most popular classical strings, are the premium classical guitar strings from D'Addario. All Pro-Arte treble strings are sorted by a highly advanced, computer-controlled laser machine that performs diameter and tension measurements to ensure precise and sonically flawless treble strings in every set. The Pro-Arte bass strings are wrapped with silver-plated copper on a multi-fiber nylon core, producing a consistent and warm yet penetrating sound. D'Addario offers a complete range of classical guitar strings for all your replacement or customization needs. This is the perfect replacement string for the D'Addario EJ47 Pro-Arte 80/20 normal tension fourth string. The normal tension makes it ideal as a replacement string or for creating custom string sets. Made in the USA for the highest quality and performance. String gauge: .042.