Mikawa Shiro Nagura 6.5oz. (183g) Japanese Natural Sharpening Stone
Approximately 95mmx45mmx24-30mm
I am not sure which layer of Mikawa shiro nagura, but it looks medium-high grit.
For razor sharpening, it is used one or two before the process sharpening by finest grit whetstone like Nakayama, Ozuku, Wakasa, etc.