These are higher grade stones designed for professionals who needs regular sharpening on their knives. Overall, these stones are best for those who don't have a lot of time to spend and need to quickly and cleanly sharpen their knives. Every Chosera sharpening stone is comes with a special Nagura stone (67 x 49 x 25 mm) to put a fine sharpening paste on the surface of the Chosera stones during sharpening process . Naniwa claims these are splash-and-go stones, but users say that soaking for a few minutes can further improve the sharpening quality.
# 400 Grit is rough stone for really dull blades or fix small chips.
# 1000 Grit is medium stone, the starting point of a regular sharpening session.
# 3000 Grit is medium fine stone, used as finishing stone for most of the kitchen knives.