Review (4/5): Should be effective if your calluses are not too thick
This device provides gentle care for the feet. I supose it should be effective for people that don't have thick calluses, and only need a file for maintainance.
In my case, another device from the same manufacturer ended up being more effective:
https://www.amazon.com/dp/ B01KLRGII4
It provides more power, which should be necessary if you have very thick skin on your feet such as myself.