Pro-Arte strings are the worlds best selling and DAddarios premium classical guitar strings. All Pro-Arte treble strings are sorted by a sophisticated computer-controlled laser machine which performs diameter/tension measurements and quality checks, insuring true sounding, precise trebles in every set. Pro-Arte basses are wound using silverplated copper on a multi-filament nylon core for consistent, warm-yet-projecting tone. Specifications Normal Tension Silverplated Clear Nylon Laser selected treble strings Basses are made with 80/20 bronze wound on nylon.