Martin Retro with Nickel-Bronze Alloy Martin Retro acoustic guitar strings are crafted from a long-lasting proprietary nickel-based alloy blend that mellows quickly to a warm vintage tone that brings out the unique - woody sounds in your guitar. These are the preferred choice of renowned fingerpicker Laurence Juber. Give your guitar the retro sound that so many have grown to love. • MFSKU 41Y19MLJ13 • UPC 729789552950