Now available in convenient three-packs. The Ernie Ball Cobalt strings represent an advancement in string technology, giving the instrument a new voice. Cobalt is more magnetic than nickel, which allows these strings to deliver maximum output, higher dynamics, more harmonic resonance, rich bass, and crisp highs. Since cobalt is more durable than nickel, the Ernie Ball Cobalt strings are longer-lasting than traditional strings. The soft and silky feel also makes string bending a breeze. Slinky Cobalt strings are nickel-free.