Strings are 010 013 017 026w 036w 046. Plain strings are comprised of a specially tempered steel. Wound strings are comprised of a patented Super Cobalt alloy wrapped around a Maraging steel hex core wire. Maraging Steel is a super alloy used for high stress applications in the aerospace and defense industries. Maker says: "The loudest, most expressive strings ever created. Provides increased output, frequency response, and strength."