This is a single/individual Ernie Ball M-STEEL guitar string. M-STEEL strings are the loudest, most expressive strings ever created. M-Steel provides an increased output, frequency response, and strength.

M-Steel, short for Maraging Steel, is a superalloy used in high-stress applications for the aerospace and defence 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 a powerful low-end response.