Description Dunlop Phosphor Bronze. Warm, rich tone, balanced response and excellent dynamics. Made in the U.S.A Dunlop Phosphor Bronze acoustic guitar strings begin with the finest materials. Custom wound onto a high carbon steel hex core, they offer players a warm full-bodied tone with incredible clarity and dynamics. Our formula creates strings that are exceptionally long-lived; they break in fast and stay bright so you can spend more time playing and less time changing your strings. Whether your finger picking or strumming your bass notes will remain focused, chords will ring out and harmonics will pop and sing.