The ceramic surface can be used to remove dead skin and calluses.
One side is coarse grit 80 for removing calluses and the other is fine-grit 150 for smoothing.
Light and easy to hold.
Rub with the coarse-grit inside of the file to remove the worst of the dead skin and calluses, etc.
Then file with the other side to refine and smooth the skin texture gently and on the more sensitive areas.
Run hot water over the file after use and dry it with a cloth.