Ernie Ball P02004 4 Sets of strings Gauges 11-15-22w-30-42-52 Ernie Ball 2004 Earthwood 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.