MinoSharp Small Grey / Black Handheld Sharpener has the special angle to sharpen Global knives. The two ceramic wheels - one rough and one medium - are positioned at a different angle from the sharpening groove. Add water so the ceramic wheels are constantly being rinsed. It cannot be used on one sided knives like the Sashimi and Deba knives and serrated knives. Instructions are printed on box. Replacement wheels available.