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, vibrant tone of these 80/20 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.