Phosphor bronze was introduced by D'Addario into string manufacturing in 1974 and has since become synonymous with a warm, bright, and balanced acoustic sound. D'Addario phosphor bronze strings are precisely wrapped with corrosion-resistant phosphor bronze around a carefully drawn hexagonal high-carbon steel core. The result is a durable, bright-sounding tone with excellent intonation. D'Addario offers a complete range of single strings for acoustic guitars to meet all your replacement or customization needs. .042 gauge phosphor bronze wrapped acoustic guitar string. Preferred for its warm, bright, and balanced acoustic sound. Perfect as a replacement string or for creating custom sets. Made in the USA for the highest quality and performance.