Double-honed for extreme sharpness, OLFA 18mm Heavy-Duty Ultra-Sharp Black Snap-Off Blades are 25% sharper than standard OLFA silver blades. These Heavy-Duty Blades are manufactured from high-quality Japanese carbon tool steel. Use Heavy-Duty Ultra-Sharp Black Blades for any application requiring superior sharpness.Eight segments per blade deliver a fresh new edge quick and easy.Long lasting and durable, use OLFA 18mm Heavy-Duty Ultra-Sharp Black Snap-Off Blades for cutting flooring, roofing, linoleum, gasket materials, and more.