Martin MSP3100 SP acoustic guitars strings 80/20 Bronze 12-54 Martin MSP3100 Studio Performance 80/20 Bronze Acoustic Guitar Strings offer a bright tone. Top artists use this 80/20 Bronze string for live performances and studio recording due to its brilliant tone out of the box,which "breaks-in" to a warmer sound. Gauges: MSP3100 Light - 12 16 25 32 42 54