Ernie Ball 2003 Earthwood 80/20 Bronze Medium Light Acoustic Strings Gauges 12-16-24w-32-44-54. Made from 80% copper; 20% zinc wire wrapped around hex-shaped tin-plated steel core wire. These strings provide a crisp; ringing sound with pleasing overtones. All Ernie Ball strings are precision manufactured to the highest standards and most exacting specs to assure consistency, optimum performance, and long life.