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It is a bit better, but not sure if it is twice as good, but to be fair I havent used either of them that much yet.

That's exactly what I did too, except I bought the 10k, then wondered about a 12, then a friend was replacing his almost new 12k as he wanted one without a base, so I ended up buying the 12 k with...

12k naniwas can be had from dieter
Schmidt, google the name and fine tools should come up. But he is on the pricey side. I think tools from Japan may sell them, and for superstones up to 10k I...