D'Addario XL Pure Nickel guitar 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 and characteristic of the D'Addario XL nickel-plated steel string line. Pure Nickel delivers classic, warmer timbres that define many genres including blues, classic rock, rockabilly, and more.