D'Addario EJ17 Phosphor Bronze Medium Acoustic Strings 3-Pack Gauges: 13-17-26-35-45-56 Gauges 13-17-26-35-45-56 Genuine phosphor bronze alloy retains flexibility as well as brilliant tone for many hours of hard play The EJ17 acoustic guitar strings feature a computer-controlled wrapping around a hex core that ensures consistency and extends life D'Addario is the world's largest manufacturer of strings for musical instruments