Very effective, but a small quirk
This machine makes removes callous material very quickly, especially with the extra grind wheels supplied.  One quirk I found:  when the machine meets resistance it will stop.  To get it started again, one must hold the power button down until the machine comes back on.  I thought mine was defective until I found the way to restart it.  It holds a charge for quite a long time, so recharging can be infrequent.
Rating: 5 stars