D'Addario Pro-Arte Classical Guitar Strings Normal tension, are D'Addario's best selling classical set, preferred for its balance of rich tone, comfortable feel and dynamic projection. D'Addario's best selling Pro-Arté set, Normal tension offers balance of volume and comfortable resistance Laser sorted clear nylon treble strings for consistent, precise intonation Precision wound basses for warm, projecting tone and the utmost consistency Made in the U.S.A. for the highest quality and performance Environmentally friendly, corrosion resistant packaging for strings that are always fresh 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.