XL Nickel Wound electric guitar strings are the standard against which all other strings are measured. D'Addario's best-selling 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. Made for 7-string guitars, this 10-59 Regular Light set takes our most popular gauge and adds an additional bass string.