Chances are you've heard it said "a sharp knife is safer than a dull one". We believe this quote originated from first hand experience and find it to be true. The Sharpmaker was Spyderco's first product, which we made and sold before getting into the knife business. It's true -- First we made things sharp, then we made sharp things. The Tri-Angle Sharpmaker (204MF) includes two sets of high alumina ceramic stones: A pair of medium-grit (brown) 7" X 0.5" (178mm X 13mm) stones for aggressive sharpening and a set of fine (white) 7" X 0.5" (178mm X 13mm) stones for professional grade finishing. The stones are triangular for sharpening Plainedges on the flat sides and SpyderEdges (serrations) on the corners. Included is a set of brass safety rods protecting the users hands while sharpening. All components snap into the self-contained ABS plastic base and lid -- ready to travel with you. Die-cut into the base are keyed slots and holes fitted for the stones. They accurately set the stone's sharpening angle at a 30° (15° each side) or 40° (20° each side) for knives and a 12.5° scissor setting. Ceramic stones, like glass, will break if dropped -- handle carefully. Use them dry, without oil, water or lubricants. To clean: scrub stones with a plastic scouring pad and powered abrasive cleaner, let air-dry. Also autoclave safe.