Will leave it for the experts to reply in more detail. As I understand it is for the progression like when sanding or polishing moving from rough grit for cutting and removing material through to a finer grit to remove deeper scratches from the previous grit. All the threads I have read on P&C and other forums recommend a similar progression from 1K for setting the bevel and progressing through to 12K and naturals for finishing. The slurry stones give additional progression something like 1 - 6 - 8 - 10 -12 - finisherLooks like an awesome setup. Why do u need 3 stones in an "ideal" kit for SE shaving?