I have used it primarily on the 4k but I don't make a habit of it. I assumed it to be used like a nagura and I think it might improve cutting slightly but it might just be power of suggestion. Most of the time if I want a slurry or want to just lightly lap my nortons, I take advantage of the fact that I have two each of the 1K, 4K, and 8K and just rub the two identical hones together. I don't use the prep stone very often anymore.