Martin M190 12-String 80/20 Bronze Light Acoustic Guitar Strings are made from a composition bronze alloy to give brilliance, clarity, and longevity of sound. The Bronze winding is ideally suited for making strings that have deep, rich basses and clear, bright trebles. Martin Strings are high-quality strings for daily use. Core and wrap wires must meet strict requirements to make the grade. Martin guitar strings are wound to precise specifications. Bronze alloy for brilliance and long life, Great price, Studio-quality performance.