I recently treated myself to the purchase of three natural sharpening stones.
In the photo above you can see, from the left, coarse grit 300, medium grit 1,200 and fine grit 6000. The stones need to be soaked in water for half an hour before use. They can be stored permanently in water, but I prefer to store them dry.
The original purchase was a sort of retail therapy, but the stones quickly became necessary luxuries.
Now, I think of them in abbreviation as: necessary.
Incidentally, the smaller object to the right is a strop, and the yellow stick in front is rubbed onto the strop to provide a polish. In my humble view, the strop is superfluous: I was persuaded of its importance by an excellent salesman.