Your guitar deserves the best accessories It deserves Ernie Ball Aluminum Bronze Medium Strings. They feature more protection and clarity than traditional bronze strings, while also providing improved corrosion resistance. Aluminum Bronze Strings are made with Ernie Ball Maraging Steel hex cores and Aluminum wrap wire which provide more pronounced lows coupled with crisp brilliant highs. The are made from a blend of copper and aluminum specifically tailored for acoustic guitar strings. Included in this package are medium gauges .013, .017, .026, .034,.046, and .056.