Jamie, I got the details from SRP and used the pm but it's better to use the link below.
Michael Cramer [ZuluGrey] <michael@zulugrey.com>
I've no idea about grit equivalent but many of the well known names (GSSixgun, Mainaman etc.) were given stones to evaluate and gave positive reviews as a finisher. One theme that was an ever-present was the ease of use when compared to other natural stones - my only experience as noted above, is with Coticules, but some of the SRP contributors who use Japanese stones were, again, very complimentary. The price is nothing like the Jnats and there is a choice of sizes - they are cut to size as with Coticules, so you get a much bigger stone at a fraction of the price.
As you can see, the stones are shipped from South Africa - mine took about 5 weeks.
Rob