XS Nickel strings have the longest life of any D’Addario electric string, plus a smooth, fast feel, thanks to the ultra-thin XS film coating.Premium nickel-plated steel wrap wire provides a bright tone with increased output, bite, and sustain.With a NY Steel core and Fusion Twist technology, XS Nickel offers greater break strength and unmatched tuning stability―staying in tune 131% better than standard electric strings.XS Nickel sets have a code on the recyclable, resealable VCI bag, which you can register to earn Players Circle points.XS Nickel coated electric strings are made in the USA―drawn to our exacting specifications at our New York production facility.