Why Heid?Since 1948 Heid Music has been providing top quality new & used instruments, repair services and music instruction. Over 1400 five-star reviews show just how hard we work to make your online experience as unique and enjoyable as visiting our stores.D'Addario XS Acoustic Phosphor Bronze strings combine their most popular acoustic alloy with advanced string coating technology, resulting in clear tone, smooth feel, and superior tuning stability – all with the longest possible string life. With its ultra-thin film coating on every wound string and a unique polymer treatment on the plain steels, XS offers the highest level of protection for maximum life. XS also features NY Steel high carbon core and plain string wire, and D'Addario's exclusive Fusion Twist, for incomparable break strength and tuning stability.