Just got them today from "Tools for working wood", good service and well packaged. I bought the two combos of all four grits, the Norton flattening stone made of silicon carbide (crystolon?) and the Norton "prep stone" which is artificial nagura stone.
THEN (before I recieved the order and after it was shipped) I read that the 8000 grit does not need it! I forgot where though. Or does it? Should I use it?