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. The EJ52 set is designed and gauged for the smaller-scale, Alto Guitar. These normal tension strings provide a rich, deep and projecting tone and like all D'Addario strings, they come in environmentally friendly, corrosion resistant packaging for consistently fresh strings, every set.