When you need to get it sharp, the 204 is all you need. Spyderco's Tri-Angle Sharpmaker includes two sets of high Alumina Ceramic stones: A pair of medium grit (dark) stones for aggressive sharpening, and a pair of fine stones (white) for professional grade finishing. There is also a set of brass safety rods to protect the user's hand during sharpening. For sharpening plain edges, the flat sides of the stones are ideal. For serrated edges, use the corners. The stones fit into keyed holes and slots molded into the polymer base and have a 40 degree and 30 degree sharpening angle for knives and a 12 1/2 degree scissor setting. A groove running the length of the stone is for sharpening pointed objects like darts, awls, and fishhooks. All components pack into the base and the lid snaps shut, making the 204 self-contained and small enough to carry in your shirt pocket. No lubrication is required during use for dry, mess-free sharpening. Includes instruction video and book.