ELECTRIC GUITAR STRING KIT XLNickel Bound Series Electric Guitar String Set, Regular Light (013 - 017 - 026 - 036 - 046 - 062) Double Ball. D'Addario XL Electric Guitar Strings have been recognized worldwide as "The Guitarist's Choice" among guitarists of all genres and styles. XL strings are wound with great precision with nickel plated steel onto a hexagonal shaped core, resulting in strings with a distinctive, brilliant tone and excellent intonation. XL158 strings are designed to be mounted on the most modern baritone electric guitars, they can also be used to lower the tuning on standard tuning guitars.