"In 1974, D'Addario pioneered the use of phosphor bronze wire for the winding of acoustic guitar strings. D'Addario phosphor bronze strings were an instant and enduring success. A more costly alloy, phosphor bronze was widely known as a durable, long-lasting material used in machine bushings and bearings. After months of searching, a wire company was located that agreed to make sample wires for testing on music strings. The results made history. D'Addario phosphor bronze strings are bright sounding and retain their brilliance longer than other bronze and brass alloys.
Round wound phosphors are available in 6 different gauges for 6 string guitar, 3 gauges for 12 string, and 4 gauges in the Flat Tops series. Flat Tops are round wound phosphor bronze strings that are lightly polished to reduce finger noise and fret wear, and are an excellent choice for noise-fee recording."