SP-4050 Martin Acoustic SP Phosphor Bronze Custom Light 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 ultra-high quality core, Martin SPs resist breakage better than any average string. 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 SPs, its primary function is to prolong string life, brightness, and enhance the tonal quality to meet the expectations of demanding performers. The 92/8 phosphor bronze wrap wire adds extra warmth to the tone, and takes away a little of the brightness for a mellower overall tone. This custom light 11-52 set is exceptionally easy to play, and gives you a little more feel and response than regular light strings, plus full tone and more volume. They are another great string from C. F. Martin, a name synonymous with fine acoustic guitars and acoustic guitar strings. Diameters: .011 .015 .023 .032 .042 .052 inches (Custom Light Gauge) From the C. F. Martin Company. Available for Order