The MM11 Retro acoustic guitar strings represent yet another quality, vintage-inspired set of strings in Martins Retro line. These strings harken back to the 1930s when nickel ruled the acoustic world. Made from Monel, a solid nickel/copper wrap, the MM11s let your acoustics natural wood tone ring through with a full low end, a high-end snap, and a solid midrange. The proprietary wrap on the MM11s is corrosion-resistant and impressively strong for long life and uncompromised tone.