A less uniform shaped koppa here but with a flat bottom and not a terribly difficult to work with shape.
Hard and fine Ozuku stone LV4.5-5 fineness and LV4.5-5 hardness. These are fast, fine and exactly what you would expect from Ozuku, just less expensive than a premium sized stone from this mine. These Ozuku koppa will need a little work to polish the face, and possibly stabilize small cracks, they are priced as such.
Being koppa there are roughly cut and do not have lacquered sides, measurements are from the widest dimensions or averages on odd shaped stones.
This stone is great for razors but less suitable for some knives. With the use of a nagura, a stone of this hardness and fineness is useful on knives like yanagi or usuba that benefit from a very fine finish on the ura (inside hollow ground side) or kireba (wide bevel) providing the steel gets along with a stone this hard. It is likely that this stone will be scratchy on the wide face of a steel with large carbides, it depends on how the steel was forged and heat treated as much as the specific alloy.