Mikawa Shiro Nagura Mejiro 5.9oz. (168g) Japanese Natural Sharpening Stone
Approximately 60mmx20-35mmx40-50mm
Koma, Mejiro, and Tenjyo are fine grit layers of Mikawa Shiro Nagura.
According to Dr. Kuniichi Tawara who is a Metallurgy doctor, and very famous Japanese sword researcher, Koma molecule is 10 to 20 microns.
It should be good for right before starting the fine grit sharpening.
For razor sharpening, it is used one process before sharpening by fine grit whetstone like Nakayama, Ozuku, Wakasa, etc.