This Martin Authentic Acoustic value pack features three sets of MA540T Lifespan 2.0 Phosphor Bronze Light guitar strings. Martin’s next-generation Lifespan 2.0 (MA540T) strings are engineered using a patented technology only available from Martin. Developed to protect the core wire and wrap wire to prevent corrosion with compromising tone – the single most important attribute of the guitar strings. Lifespan 2.0 strings ensure they will sound better, longer than any other extended-life string on the market. Enjoy excellent tuning stability, great playability and feel, and superior reliability with authentic tone!