Ernie Ball EB2722 Slinky Cobalt Electric Guitar Strings Ernie Ball 2722 Cobalt Hybrid Slinky Electric Strings are a perfect match for those who like the ability to combine the combination of Super and Regular Slinkys. The Cobalt Series is clearly an improvement on its classic nickel-wound counterpart giving the player increased sustain, clarity and output. In addition, they resist sweat and moisture better and have unmatched flexibility when compared to other nickel wound strings.