Ceramic sharpening whetstone set. Ceramic is harder material than normal stones and it reduces your time for sharpening.
Rough #400 is good for repairing small chips and making the edge thinner.
Standard #1000 is good for usual maintenance.
Fine Whetstone #3000/#6000/#10000/#13000 is to be used after a standard whetstone. For those seeking more sharpness and better maintenance.
Video: How to use sharpening stone.