WUSTHOF Ceramic Whetstone. Length 15 cm, wide 5 cm, height 2.5 cm. Coarse and Fine Grain (J 400 / 2000). The optimum solution for sharp knives. Suitable for use with water or oil. Alternatively you can moisten the whetstone with oil. Once you have decided to use oil, however, you must no longer moisten it with water.