Ernie Ball Classic Rock N Roll Slinky electric guitar strings are made from pure nickel wire wrapped around hex-shaped, high-carbon steel core wire. The plain strings are made of specially tempered tin plated high-carbon steel. Pure nickel electric guitar strings were the standard in much of the ‘50s and ‘60s and produce a warm, rich tone. Gauges .009, .011, .016, .024, .032, .042.