Pumice stones - lava natural stones - if you have annoying cornification, you will quickly appreciate this natural stone.
It has a long shelf life and removes calluses easily and in a simple manner. Since this is a purely natural product, the size can vary. Pumice stone is a very light, porous volcanic rock that forms during explosive eruptions.
If you soak the pumice stone in bleach every two months, it will keep it clean and hygienic for many years.