This package contains six packs of Martin MA140 Authentic Acoustic SP 80/20 Bronze Light 12-54 strings. Designed for the performer, these strings always withstand rigorous practice and performance plans. We start with our core wire with the highest tensile strength and then tinned it on all six strings for added corrosion resistance. Because what you dont see matters. Coupled with our highest quality winding wire, you get a consistent true tone you can rely on song by song. Available in 80/20 bronze and 92/8 phosphor bronze. Martin Authentic Acoustic SP strings offer excellent tuning stability, corrosion resistance and great playability.