The D'Addario XSAPB1047 is a coated phosphor bronze acoustic guitar string set in an extra-light gauge, .010-.047. An ultra-thin XS film coats the wound strings while a polymer treatment protects the plain steels, extending string life while keeping a smooth feel. The strings use phosphor bronze wrap wire over D'Addario's NY Steel core for warm, balanced acoustic tone and tuning stability. Made in the USA.