D’Addario Guitar Strings – XS Phosphor Bronze Coated Acoustic Guitar Strings are designed to provide maximum life with a smooth feel and exceptional tone. These strings feature an ultra-thin film coating on every wound string and a unique polymer treatment on the plain steels, offering the highest level of protection. The XS Phosphor Bronze strings also have a NY Steel high carbon core and plain string wire, along with the exclusive Fusion Twist for incomparable break strength and tuning stability. With a gauge of 13-56 Medium, these strings are perfect for 6 string guitars. Experience the innovation of XS, the most advanced coated strings ever created.