XL Nickel Wound electric guitar strings are the standard against which all other strings are measured. D'Addario's best-belling electric set, XL Nickel has been revered by players everywhere since 1974. Made with a high carbon steel core and nickel-plated steel wrap wire, XL Nickel strings have a bright, versatile tone, ideal for a wide variety of musical styles. With its super flexibility and biting tone, this 09-54 Super Light set is one of D'Addario's best selling 7-string sets.