Ernie Ball Nickel Wound 12 String Slinky 8-40 strings for electric guitar. The wounded strings of Ernie Ball slinky made nickel plated steel and the core wired around the hexa core. The plain strings are thin plated carbon steel wires. The strings gauge 008*.008, .010*.010, .014*.008, .024w*.011, .032*.017, .040*.022w