EJ43, light tension - Great for beginners or experienced players with a lighter touch, they provide ease of play without sacrificing rich tone. 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.