The Naniwa Professional line (previously known as the Chosera line) are super hard splash and go stones. These stones are slow wearing, fast cutting and HARD. They have a higher amount of abrasives and less binder than other lines from Naniwa, and are one of the best lines of stones money can buy in our opinion!
This is our favorite 400 that we've used. It will cut an edge in on a quite dull knife without effort, and leave great tooth for your edge if you don't polish it too long afterwards on higher grits. This paired with a quick touch on a 1k and then an even quicker stop on the 5K or equivalent will leave you with a refined enough edge to maintain a good cutting feel, but all the tooth needed for tomatoes, peppers, sinew and silverskin. Not to mention that this stone have a very consistent grit making it great for coarse work to set a foundation to polish on top of, where cheaper coarse grit stones tend to have a more inconsistent grain size and can cause unsightly feep scratches that are more difficult to work out on subsequent higher grit stones. All around, a shop favorite!