This is similar to what I am using. At first I thought going from the Rika 5k to the Gesshin 5k was a waste, but the Gesshin provides a finish closer to a 6+k. I love the stone, although it is not fast.
Rick, I've got it.
I did an email search and Stu mentioned that that the Ceramic Series and the Renge Series look exactly the same but the Ceramic is harder:
<<Funny, the actual Sigma Ceramic looks the same, works the same but is harder still.>>