D'Addario was the first company to use phosphor bronze in the manufacture of its acoustic guitar strings in 1974. Today, guitarists around the world play phosphor bronze, now considered the gold standard for guitar strings acoustic, because of its warmth and splendid sound balance. Our pioneering Phosphor Bronze acoustic guitar strings are constructed with precision-wound phosphor bronze binding over a carbon-rich steel core to produce all the sonic versatility required to accommodate all styles and registers of acoustic music. . Ideal for drop tunings, this 14-59 Heavy set benefits from the strongest acoustic guitar gauge in our entire range, providing maximum tension and resistance, as well as the most powerful and resonant tones.