Irwin IRW10504241 - Bi-Metal Trapezoid Knife Blades Pack of 10 Irwin Bi-Metal Trapezoid Knife Blades combine the best of two metals electro-welded together. - 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. - This blade stays sharp up to 3 x longer than standard blades. The high-speed steel edge, and heat treated to greater hardness for longer life and edge sharpness. - Fits all standard knives