Since D'Addario introduced Phosphor Bronze strings in 1974, they have been synonymous with warm and well-balanced tone. XT Phosphor Bronze resonator guitar strings offer that and more, with improved break resistance, better pitch stability, and longer life than standard resonator strings. The XT coating provides advanced corrosion resistance, while maintaining the warm tone and natural feel of an uncoated string. Beneath the coating, these XT resonator guitar strings are built with an NY steel core, phosphor bronze wrap wire, and Fusion Twist technology, delivering tonal versatility with added resilience. This 16-56 gauge resonator set is optimized for resonator guitars.