D'Addario is on a mission to create the finest coated acoustic strings the world has ever seen. One such result of that labor, the XS Phosphor Bronze series acoustic strings feature an NY Steel hexagonal core with a wrap wire of phosphor bronze to deliver balanced warmth and enhanced harmonic content that span the entire neck. Not only that, but XS Phosphor Bronze acoustic guitar strings feature an ultra-thin film coating for added protection against sweat and grime. This coating give the strings long-lasting great tone — some of the longest lasting in the D'Addario catalog — and dramatically extended playtime between string swaps. And if you ask us, they feel great under the fingers, too. You also get D'Addario's Fusion Twist technology and digitally controlled winding for increased tuning stability and 1:1 consistency from set to set. Sweetwater players agree: if you're looking for D'Addario coated acoustic strings that sound great and give you double-digit hours of playtime between sets, XS Phosphor Bronzes are a clear winner.