D"Addario Phosphor Bronze Acoustic Guitar strings are acclaimed worldwide for their superb, long-lasting tone. Phosphor Bronze was introduced to string making by D"Addario in 1974 and has become synonymous with warm, bright, and well-balanced acoustic tone. D"Addario"s most popular acoustic guitar strings.Custom Light gauge (.011"-.052") Warm, bright, and balanced tone Phosphor bronze wound Long lasting