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.