Irwin 10504243 Bi-Metal Blades x100 Pcs The edge of the 10504243 blades are made from high-speed steel, which is much harder than standard carbon steel, and has been shown to last up to 3x longer in user trials on plasterboard, drywalling, roofing, insulation, flooring and other heavy-duty materials. The bulk of the blade is made from spring steel, which can resist pressure applied from the side without snapping. The safest blade to use is generally a sharp one - as it takes less effort to cut, and therefore greater control can be maintained. FEATURES Fits all standard knives Stays sharp up to 3x longer than standard blades High-speed steel edge Heat treated to greater hardness for longer life and edge sharpness SPECIFICATION Quantity: 100