Referred to as Custom Light, EJ13 strings are a D'Addario original hybrid gauge and a comfortable compromise for players who want the depth and projection of light gauge bottom strings, but slightly less tension on the high strings for easy bending. 80/20 Bronze, commonly referred to as brass, is the original acoustic string alloy selected by John D'Addario Sr. and John D'Angelico in the 1930s. 80/20 Bronze strings are popular for recording due to their crisp, deep and projecting tone and appeal to many traditionalists and vintage enthusiasts for their historical significance. All D'Addario acoustic strings are wound on a hexagonally shaped, high carbon steel core, resulting in long lasting, bright sounding tone with excellent intonation.