XS is the most innovative coated string ever created. Play more than you ever thought possible and sound better for longer thanks to D'Addario's highest level of protection yet. Experience maximum life, a comfortably smooth feel, and a long-lasting tone that's always ready-to-play. Coated with our groundbreaking XS coating, THESE premium strings provide the longest Life of any D'Addario Electric guitar string. With XS Nickel, you can have maximum string Life and a smooth, fast feel and a top exeptional wound tone.