D'Addario XS Acoustic Phosphor Bronze strings combine our most popular acoustic alloy with our most advanced string coating technology, resulting in clear tone, smooth feel and superior tuning stability - all with the longest possible lifespan of the ropes. With its ultra-thin film coating on each wound string and a unique polymer treatment on the raw steels, XS offers our highest level of protection for maximum lifespan. XS also features a high-carbon NY Steel core and single string, as well as our exclusive Fusion Twist, for unrivaled breaking strength and tuning stability. XS is the most innovative coated string we've ever created. Never faint!