Japanese Wet Stone 10,000 Grit from Satake is a whetstone for maintaining already sharp knives. Best used in combination with a coarser stone of at least 1200 grit. Whetstones are graded according to grit, or degree of fineness, which is determined by the purpose of the grinding. Satake sharpening stones are color coded to easily show which grit they have, and the packaging matches the color of the stone for easy identification.