Review (5/5): Very effective, but use carefully
The best way to use this is to soak your feet first for 5-10 minutes in warm water. (A foot bath is ideal.) When the callus is softened, shave with a reasonably light touch. You can apply some pressure, but don't get too aggressive. Better to go over it a few times than to risk cutting your foot. The ball of your foot can take more pressure, but be more careful with your toes and heels. You'll be very happy with the results, especially if you tend to develop dry heels.