Naniwa Chosera 600 Grit Whetstone w/Base
The Naniwa Chosera series of stones are an elite, Japanese domestic product only. They are very hard to source outside of Japan. They are the same material as the Pro, but are thicker and come with a Nagura and base, representing much better value for money.
They are a fast stone, great for Kasumi, and are officially splash and go, but benefit from a quick soak before use.