Ernie Ball Ernie Ball Earthwood Mandolin Light Loop End 80/20 Bronze Acoustic Guitar Strings are made from 80% copper, 20% zinc wire wrapped around hex shaped tin plated steel core wire. The most popular acoustic guitar strings provide a crisp, ringing sound with pleasing overtones. Gauges .009, .013, .022w, .034 mandolin light loop end 80/20 Bronze acoustic guitar strings are made from 80% copper, 20% zinc wire wrapped around hex shaped tin plated steel core wire. The most popular acoustic guitar strings provide a crisp, ringing sound with pleasing overtones. Gauges .009, .013, .022W, .034.