Irwin Tools 2086405 Bi-Metal Snap Blades 18mm, 50EA/ Pack Bi-metal snap blade construction combines 2 types of metal, spring steel and high-speed steel Spring steel allows the snap blade to bend without accidentally breaking Also helps ensure that the utility knife blades snap cleanly on the score every time High-speed steel delivers a hardened cutting edge that stays sharp Includes 50 blades Bi-Metal snap blades are produced through a patented process of combining two types of metal, spring steel and high spped steel. Spring Steel allows the blade to bend without accidentally breaking. It also ensures that the blade snaps cleanly on the score every time. High-Speed Steel Delivers a hardened cutting edge that stays sharp 3x longer than traditional carbon blades.