Gauges 10-13-17-30-42-52 Ernie Ball 2008 Earthwood Rock and Blues Acoustic Guitar strings are crafted from 80% copper, 20% zinc wire wrapped around hex shaped tin plated steel core wire. The most popular acoustic provides 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.