Developed in collaboration with John Mayer, Ernie Ball Earthwood Bell Bronze strings have been carefully crafted to meet John's exacting standards, providing a new voice for your acoustic guitar. Inspired by alloys used traditionally for bells and cymbals, Ernie Ball's proprietary Bell Bronze acoustic guitar strings offer a richer, fuller sound than any other string in our catalog. These strings will breathe new life into your guitar! Gauges .010, .014 .020w, .028, .040, .050