Martin MM12PK3 Retro Acoustic strings feature proprietary and naturally corrosion-resistant Monel wrap wire to deliver true, consistent tone with enhanced longevity. This solid nickel/copper alloy blend provides a reduced pick attack that allows your guitar’s tonewoods to be heard, not overshadowed. Retro strings also sound great plugged in for your acoustic-electric. This is a pack of three sets of light strings with gauges 12–53.