These strings feature a round core, a special winding process for balanced tone and feel across strings, and green silked ends.
 
GHS says:
 
GHS is proud to release Balanced Nickel strings for bass guitar, a combination of traditional string materials and modern string design. Wound over a round steel core with a pure nickel (nickel 205) final cover, Balanced Nickels have the same number of wraps from string to string. This yields a tone that is deep but focused, with an extremely even response, no matter where you are on the fretboard. The end result is a balance between tension, flexibility, tonality and playability.
Why Should You Play Balanced Nickels?
You want that vintage bass guitar sound, with a modern twist
You're looking to unlock the full tonality of your bass
You want the same tonality across the entire fretboard