EJ49, normal tension, is D'Addario's best-selling classical set containing custom extruded black nylon trebles, preferred for its balance of rich tone, comfortable feel and dynamic projection. All Pro-Arté treble strings are computer controlled by an X-Y laser microscope which performs diameter and tension measurements, ensuring true-sounding, precise trebles in every set. Pro-Arté basses are wound using silver-plated copper on a multi-filament nylon core for consistent and warm, yet projecting tone.