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. Pro-Arte basses are wound using silver-plated copper on a multi-filament nylon core for consistent and warm, yet projecting tone. EJ44, extra hard tension, is optimised for maximum string resistance and projection without compromising tone.