M-Steel Regular Electric Guitar Strings are made of M-Steel, short for Maraging Steel, is a superalloy used in high stress applications for the aerospace and defense industries. The wound strings are comprised of a patented Super Cobalt alloy wrapped around a Maraging steel hex core wire, producing a richer and fuller tone with powerful low end response. M-Steel plain strings are comprised of a specially tempered steel for maximum fatigue resistance. A patented winding of steel around the ball end of the plain strings reduces slippage, breakage and stays in tune better than conventional plain strings.