Honyama sharpening stone. Made from a naturla fragments of lime sandstone, planned flat on one side, it cuts very well and produces a fine slurry cutting at between 6000-8000 grit. It can only be used with water! As it is a natural product it can vary in size and may have natural imperfections.
As a natural stone the sizes vary but are between 10 - 20mm x 70 - 90mm x 100 - 140mm