Phosphor Bronze has been used for string manufacturing since 1974 and has since represented a warm, brilliant, and balanced sound. D'Addario's Phosphor Bronze strings are made by winding corrosion-resistant Phosphor Bronze wire around a hexagonal carbon steel core. The result is a durable string with a powerful tone and excellent intonation. It delivers a warm and well-balanced acoustic sound. Gauge: .010, .014, .023w, .030, .039, .047.