The perfect replacement string for the D'Addario EJ47 Pro-Arte 80/20 Normal Tension fourth string. Pro-Arté Nylon Singles are the perfect replacement string or for creating custom classical guitar string sets. Pro-Arté the world's most popular classical strings are D'Addario's premium classical guitar string sets. All Pro-Arté 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.