The J4503 is the perfect replacement string for the D'Addario EJ45 Pro-Arte Normal Tension classical guitar string set. Pro-Arte, the world's most popular classical strings are D'Addario's premium classical guitar string sets. 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. The perfect replacement string for the D'Addario EJ45 Pro-Arte Normal Tension third string Laser sorted clear nylon treble strings for consistent, precise intonation Normal Tension Perfect for replacement string or customized sets Made in the U.S.A. for the highest quality and performance