Product DescriptionD'addario xl pure nickel strings look back to the '50s, when nickel was the primary alloy found in electric guitar strings. into the '60s, these pure nickel strings would be supplanted when guitarists required brighter tone and enhanced magnetic properties/characteristic of the d'addario xl nickelplated steel string line, pure nickel delivers classic, warmer timbres that define many genres including blues, classic rock, rockabilly, and more.From the ManufacturerEPN21's combine the playability of D'Addario's most popular jazz light gauge set with a warmer, vintage tone.D'Addario XL Pure Nickel strings look back to the '50s, when nickel was the primary alloy found in electric guitar strings. Pure nickel strings would be supplanted by nickelplated steel in the '60s when guitarists required brighter tone and enhanced magnetism. Pure Nickel brings back the richer, warmer timbres found in traditional blues, classic rock, rockabilly, and more.D'Addario, the world's largest manufacturer of musical instrument strings, is known as The Players Choice with a reputation for unsurpassed quality and consistency. D'Addario's innovative packaging reduces waste and provides protection from corrosion. All D'Addario strings are manufactured in the U.S.A. using proprietary, digitally controlled, state-of-the-art machinery for unmatched performance, set after set.