Wound Strings are 80% copper, 20% zinc wire wrapped around hex shaped tin plated steel core wire • Plain strings are made of specially tempered tin plated high carbon steel • The most popular acoustic guitar string alloy provides well balanced projection with crisp pleasing highs • Element Shield Packaging Prolongs string life and keeps strings as fresh as the day they were made • Made in California, U.S.A. Featuring the finest and freshest materials.