Martin M2000 Marquis 92/8 Phosphor Bronze Extra Light Acoustic Guitar Strings are made with a unique composition that gives brilliance, clarity, and longevity of sound. The phosphor bronze winding alloy is ideally suited for making strings that have deep, rich basses and clear, bright trebles. Marquis series strings also feature silk winding at the ball end to protect the bridge and bridge plate, this is especially useful on vintage or delicate guitars.