The Martin SP 7100 Phosphor Bronze Lifespan Coated Light Acoustic Strings - 3-Pack means you'll never be caught without some backup strings or spares for a fellow band member. Martin SP Lifespan acoustic guitar strings are treated with Cleartone proprietary technology to bring you the longest possible string life without sacrificing tone or natural feel. Recommended for all types of musical styles these strings are designed to repel the oils and dirt that can deaden strings.Phosphor Bronze strings are bright, but slightly warmer sound than 80/20 bronze when first put on the guitar and offer consistent tone over time. Martin SP Lifespan acoustic guitar strings are used by Martin on the majority of its production guitars. Martin SP Lifespan with Cleartone proprietary technology provides a rich, full tone with the added benefit of longer strings.Phoges: 12-16-25-32-42-54.