Ernie Ball Earthwood 80/20 Bronze Acoustic Guitar Strings are made from 80% copper, 20% zinc wire wrapped around hex shaped brass plated steel core wire. These acoustic guitar strings provide a crisp, ringing sound with pleasing overtones. Gauges .010 - .010, .014 - .014, .022w - .009, .030 - .012, .040 - .018p, .048 - .028