Adamas Strings for Acoustic Guitar Nuova phosphor bronze coated - Also suitable for people with allergy (1717NU)Adamas Phosphor Bronze coated Solid brass ball end, E6 and A5 string core and winding each with identical diameter Composite gauging: A5, G3, and H2 string thinner than gradations from other manufacturers. High end Premium Phosphor Bronze, coated Ultra thin nano coating below 1 micron = 0. 001 mm is applied to winding wire and core before the string is wound. Alloy specially modified for the coating with a high copper content. Warm, rich, earthy tone