Everlast is the long-life treatment from Ernie Ball. Its a nano-treatment applied to the surface of both the core wire and outer wrap wire which repels moisture, oils and grime. The steel hex core wire is brass-plated which adds to and enhances the bright, warm tone of these phosphor bronze strings. They dont feel remotely coated yet that resounding clarity is retained for weeks and weeks. Great strings with an unmistakable, archetypal Ernie Ball acoustic tone. Ernie says: Engineered to maximize output and clarity, Ernie Ball Cobalt Slinky Guitar Strings are the latest innovation in string technology. Seeking to provide guitarists and bassists with a new voice, Cobalt strings provide an extended dynamic range, incredible harmonic response, increased low end, and crisp, clear highs. Cobalt provides a stronger magnetic relationship between pickups and strings than any other alloy previously available. Cobalt Slinkys are also soft and silky to the touch, making string bending a breeze.