From Ernie Ball:

Ernie Ball Cobalt Slinky Electric Bass Strings are engineered to maximize output and clarity. These strings provide an extended dynamic range, incredible harmonic response, increased low end, and crisp, clear highs. Cobalt Slinky strings produce a stronger magnetic response with pickups than any other alloy previously available. Cobalt Slinky bass strings are also wound for added flexibility, making string bending a breeze. Gauges .045, .065, .080, .100, .130