Martin SP-3100 Light Gauge Bronze Acoustic Guitar Strings Martin's SP (Studio/Performance) acoustic guitar stings are specifically engineered for live and studio performances, and where maximum string life is demanded. The SP Series is a high performance acoustic guitar string developed through research conducted by Martin with specialty steel producers. With the development of an industry leading, ultra-high quality core, Martin SP's resist breakage better than any average string. The wound strings are made with a premium, high carbon, high strength hex core wire. In addition, the cores of the wound strings and the plain, bare stings are both plated with a smooth, acoustic bronze finish. This golden bronze finish does more than just enhances the looks and feel of the SP's, its primary function is to prolong string life, brightness, and enhance the tonal quality to meet the expectations of demanding performers. And being wound with 80/20 bronze alloy wrap wire, these strings have a naturally bright tone which softens and mellows slightly as it ages, yet it never looses its brilliance. This light gauge set is easy to play, and lets you play longer and harder. Martin MSP-3100s are another great guitar string from C. F. Martin, a name synonymous with fine acoustic guitars and guitar strings. Diameters: .012 .016 .025 .032 .042 .054 inches (Light Gage) From the C. F. Martin Company. Available for Order