Ernie Ball Cobalt Power Slinky Bass Set, .055 - .110 Cobalt provides a stronger magnetic relationship between pickups and strings than any other alloy previously available Patented technology brings a new definition to low end capabilities Soft and silky to the touch Element Shield Packaging Prolongs string life and keeps strings as fresh as the day they were made Made in California, U.S.A. Featuring the finest and freshest materials.