Ernie Ball Everlast Coated acoustic guitar strings use groundbreaking nanotechnology that repels unwanted moisture and oils that negatively impact your tone. A proprietary treatment is applied to both the inner hex core and outer wrap wire to provide ultimate protection without compromising tone or feel. Made from 92% copper, 7.7% tin, 0.3% phosphorus wire wrapped around brass plated hex shaped steel core wire, Phosphor Bronze strings produce warm rich bass tones with clear bright trebles. Gauges .013, .017, .026, .034, .046, .056 • MFSKU PO2544 • UPC 749699125440