D'Addario was the first to use Phosphor Bronze in acoustic guitar strings in 1974. Today, Phosphor Bronze is played throughout the world and is considered the standard in acoustic strings, thanks to its beautiful sonic balance and tonal warmth. D'Addario's pioneering Phosphor Bronze acoustic guitar strings are precision-wound with phosphor bronze wrap wire over a high-carbon steel core, providing tonal versatility suitable for all acoustic styles and musical genres. Suitable for drop tunings, the 14-59 Heavy gauge set is the heaviest acoustic gauge D'Addario offers, providing the most tension and resistance, with the boldest, most resonant tone.