La Bella VSA1252 Vapor Shield Acoustic Guitar Strings, Light 12-52 String Gauges: . 012, . 016, . 022W, . 031, . 041, . 052; Tension: Light Phosphor Bronze Wound & Plain Steel treated with Ionic Vapor Process Slick mutated surface is resistant to oil and grime Made in the USA with American Wire Packaged using MAP Technology (Modified Atmosphere Packaging) to prevent tarnishing and ensure freshness