Gibson 80/20 Bronze Acoustic Guitar Strings help bring out the true acoustic sound of your guitar. The strings are wrapped with an 80% copper, 20% zinc alloy, which delivers bright and crisp tones while maintaining the perfect balance of authentic acoustic tone & playability. A favorite in the studio, these strings are ideal for all Gibson Acoustic body designs and all playing styles. Medium Gauge: .013 .017 .026 .035 .045 .056