Test winner of the large sharpening stone test by Stiftung Warentest. The Kai Shun combination whetstone was awarded the test winner title in the sharpening stones category with a score of 2.0 in Stiftung Warentest 01/2010. With its two sides, the combination whetstone from Kai offers a 300 and a 1000 grit. The finer grit allows for easy resharpening of blades by rubbing them evenly under light pressure over the wet stone. The coarser side of the Kai whetstone is recommended for removing small cosmetic defects from the blade. Before using the Kai whetstone, it should be fully submerged in water for about 10 minutes. During sharpening, a light film of water should always be present on the surface of the Kai whetstone. The Kai whetstone can be used for both single-bevel and double-bevel knives.