Jig-saw blade bi-metal. Century bi-metal jig-saw blades offer a carbon alloy backbone and cobalt alloy high speed steel teeth for maximum performance. Carbon alloy backbone allows for blade flexibility and absorbs chock when cutting difficult materials. Cobalt high speed steel teeth offer best wear resistance in all types of cutting materials. Century bi-metal jig-saws are designed for performance, lasting 5x longer than carbon alloy blades.