Gauges 13-17-26-35-45-56.

Martin SP Studio/Performance Series acoustic guitar strings are ideal live, in the studio, or wherever maximum string life is desired. The creation of these high-performance strings is a result of research done in cooperation with specialty steel producers. Due to the development of an industry leading ultrahigh-quality steel core, Martin SP strings resist breakage better than average guitar strings. In addition, both the core wires and the plain strings are plated with a smooth, acoustic bronze finish. Though this golden bronze finish does enhance the beauty of your guitar, its purpose is much more functional--to prolong brightness, string life, and superior tonal quality to meet the high expectations of demanding musicians.