The Coated Phosphor Bronze are D’Addario’s most popular type of strings for acoustic guitar that utilizes EXP coating for extended lifespan. Since D’Addario introduced Phosphor Bronze guitar strings in 1974, they have been synonymous with warm and well-balanced acoustic tone. Pioneered in 1974 and still revered today, Phosphor Bronze has become synonymous with warm, well-balanced acoustic tone. D’Addario Phosphor Bronze strings are precision wound with corrosion-resistant phosphor bronze onto a carefully drawn, hexagonally shaped, high carbon steel core. The result is long-lasting, bright sounding tone with excellent intonation.