Martin MA500T Phosphor Bronze Treated 10-47 Extra Light, 12-String Guitar StringsNext generation Martin Authentic Acoustic Lifespan 2. 0 strings are engineered using a new, patented anti corrosion treatment only available from Martin. It protects the core and wrap wire to prevent corrosion without compromising tone or feel. Martin's impeccable standards for acoustic guitar tone are embedded in their string design and precision manufacturing process. Gauge: Extra Light 12 String E: . 010 . 010 B: . 014 . 014 G: . 023 . 010 D: . 030