Gauges 12-16-25-32-42-54.

Martin 3100 Coated SP Plus 80/20 Light Acoustic Guitar Strings are specially coated to offer you clear, rich, and long-lasting sound. Martin Extended Life strings also deliver numerous benefits, including protection from moisture, salts, perspiration, and other contaminants. In addition, the new SP+ coating helps insulate the wrap wire to prevent corrosion between the core and the wrap wires. Martin uses computerized equipment in a climate-controlled environment to verify the high tensile strength of all incoming wire prior to manufacture. The brass wrap is then carefully spun onto the core wire for the 4 wound strings of each set. Martin SP+ strings use the same special brass-plated core wire that is incorporated in the innovative SP string, but the brass wrap on the 4 wound strings is specially coated. The coated string surface has a smoother feel for faster playing.