Darco by Martin Guitars.. Pay Less. Play More. The Darco line of acoustic strings promises quality, tone, and value in every pack. They are designed for the pros and priced for the working musician so every guitar player can afford to change their strings as often as needed to keep their guitar sounding new all the time. Darco D220 Phosphor Bronze Acoustic Guitar Strings, .012- .054 • MFSKU D220 • UPC 729789555531