Naniwa synthetic extra-fine Nagura. This is especially recommended for Super Stone 5000 - 10000 stones for best results. When choosing the coarseness of the Nagura, the basic rule of thumb is; to choose at least the same grit or finer than the whetstone you are using.
Grit: #10000
Long: 60 mm
Wide: 30 mm
Thick: 20 mm
Weight: 78 g