The Martin Era™ Phosphor Bronze Treated Acoustic Guitar Strings in Medium gauge (13-56) offer rich, full-bodied tone with enhanced durability and long-lasting performance. Their proprietary corrosion-resistant treatment helps the strings stay vibrant and responsive through extended playing, whether you’re strumming big chords or digging into dynamic fingerstyle work. With warm lows, articulate mids, and bright, balanced highs, these phosphor bronze strings deliver smooth playability and reliable tension that many players prefer for robust acoustic expression. Built to the quality standards players expect from C.F. Martin & Company, the Era™ 13-56 set is a versatile choice for gigging, rehearsing, or recording with confidence.