Ernie Ball M-Steel Super Slinky Set, .009 - .042 Superior magnetic attraction providing the most expressive strings ever created Dynamic frequency response with increased output and added strength Super Cobalt alloy wrapped around a Maraging steel hex core wire, producing a richer and fuller tone with powerful low end response Made in California, U.S.A. Featuring the finest and freshest materials. Element Shield Packaging Prolongs string life and keeps strings as fresh as the day they were made