Universal diamond grindstone for polishing edges, removing hardened steel from stone damage, and reducing aggression in the tip and tail of the ski. The Universal stone does it all, if you're looking to have only one file in your box.
The diamond grindstone is used after you have set the edge up to polish it, for extra sharpness. It can also be used to grind away rust.
You can combine a coarse and a fine grindstone or have a medium one.
