Gauges 9-12-20w-26-36-46. Ernie Ball 2051 Earthwood Acoustic Guitar Strings are crafted from 80% copper, 20% zinc wire wrapped around a nylon core for a mellower sound. These strings also lessen tension making instruments easier to play. All Ernie Ball strings are precision manufactured to the highest standards and most exacting specs to assure consistency, optimum performance, and long life.