Elixir strings are coated in a unique and patented way to protect wound strings from contaminants and corrosion. A flexible, strong, yet micro thin polymer tube defends the string. It can be thought of as a heat shrink tube that's thinner than a human hair. Nothing (including the coating) gets between the windings. 

Medium gauge Acoustic Guitar Strings, 0.13 - 0.56. These particular strings have a balanced tone and smooth response. They also feel comfortably smooth and reduce finger squeak.