Martin Retro strings are the real deal. Not an imitation. With Martin Retro strings, you get one tough set that offers true, consistent tone and sounds like nothing else on the market. Martin’s solid nickel/copper alloy blend provides a reduced pick attack that allows the guitar’s tonewoods to be heard, not overshadowed. Martin’s proprietary Monel wrap wire is naturally corrosion resistant, so you can play them for a long time with nothing to get in the way of your music. Discover your guitar’s true voice. Retro strings offer enhanced longevity with warm natural tone, and they sound great plugged in. .013, .017, .026, .035, .045, .056 Gauge with 190.9 tension.