Lenox Hand Hacksaw Blades feature bi-metal construction, a spring steel back, a tooth hardness of Rc64-66, and an M-2 high speed steel cutting edge. These blades are shock and shatter resistant, have high heat resistance, and are virtually unbreakable. They are safer than solid high speed steel blades and outperform carbon steel up to 10 to 1. They provide a freer cutting action and smoother cut. This model has 18 teeth per-inch and measures 12 inches long by 1/2-inch wide. Use for Cutting Heavy Metal. 1 Blade per Package.