D'Addario 3D pack gives you three sets of acoustic guitar strings, saving you just under a fiver! D'Addario introduced Phosphor Bronze strings back in the 70s, and since then has become one of our most popular selling sets of strings. It gives you a warm and bright tone. D'Addario Phosphor Bronze are precision wound using corrosion resistant phosphor bronze, on to a hexagonally shaped high carbon steel core. This combination gives you a bright, long lasting tone with excellent intonation. EJ15 Gauge – 10, 14, 23w, 30w, 39w, 47w.