XS Nickel coated electric guitar strings provide the longest life of any
 D’Addario electric guitar string. Coated with our groundbreaking XS 
coating, these premium electric strings attain maximum life and a 
smooth, fast feel without dampening their outstanding tone. Constructed 
with a NY Steel core, reformulated nickel-plated steel wrap wire, and 
Fusion Twist technology, XS Nickel strings boast superior strength and 
tuning stability, plus richer harmonics, greater clarity, and remarkable
 definition with every sweep, slide, and bend. This 11-49 Medium gauge 
set provides increased volume, with slightly more tension and 
resistance.