This is the top of the line from NANIWA. Great for experienced sharpeners who can maintain a consistent angle, these stones cut fast and stay flat for a long time. They're splash and go so no need for soaking. Once called chocera stones, these are exactly the same without the plastic base.
All of the whetstones sold at the shop are Waterstones, do not put oil on any of them, you will ruin your stone. Holding the knife at a consistent angle while sharpening is one of, if not, the most important thing to consider when sharpening; thus, maintaining a flat stone is of equal importance. Pick up a truing stone to maintain a flat stone in order to achieve the best results.
If your stones are super worn out and completely concave using a truing stone will take hours to flatten them. Consider purchasing a King flattening stone to get the job done quicker.