The Heavy-Duty Utility Blades from Warner are professional quality. They are produced with a proprietary grinding process, using the highest quality materials. The blades come with with two notches and center hole. Blades are made of 0.025 in. premium grade carbon steel construction, which produces a harder, sharper edge. They fit is most, if not all, standard utility knives. 50 Blades total in handy plastic dispenser.