Ernie Ball Hybrid Slinky Flatwound Bass Strings combine the silky feel of traditional flats with the power of Cobalt. Cobalt strings are made with a modern alloy formulation that attracts the magnets in your pickups better than other alloys, delivering higher output, better sound, and longer string life. Featuring a SuperBright Cobalt ribbon wrap, Cobalt under-wrap, and an optimized hex-core/wrap ratio, Ernie Ball Slinky Flatwound bass strings combine the smooth feel of flats with the growl and brightness of rounds.