D'Addario XT Acoustic Phosphor Bronze strings combine our most popular acoustic alloy with an advanced corrosion resistance treatment on every string in the set, preserving the natural tone and feel of uncoated strings.Stand the test of time with strings that endure. D’Addario XT strings combine our strongest high carbon steel with an advanced corrosion resistance treatment on every string in the set, giving you enhanced break resistance and unyielding pitch stability—all while preserving the tone and feel of your favorite uncoated strings. These strings are made to stay, with uncompromising performance that never fades away.