Gauges 14-18-27-39-49-59. D'Addario Phosphor Bronze EJ18 Heavy Acoustic Guitar strings are acclaimed worldwide for their great, long-lasting tone. Phosphor Bronze was introduced to string making by D'Addario in 1974 and has become synonymous with warm acoustic tone. D'Addario is the world's largest manufacturer of strings for musical instruments. Many top guitarists won't play any other brand. Regardless of playing style, D'Addario has a set of strings that's right for acoustic guitar.