Review (4/5): Great Idea of the interchangeable heads.
This is fine for my heels, but really didn't do too great on my front callouses. I have bunions, so I get thick callouses easily around my toes. I definitely like the rechargeable over the alkaline batteries. I've had grinders with different wheels before and there was more of a difference between the course and fine wheels.
I do like that the heads switch out mechanism is easy to use. I have about half a charge when I got it and it did charge to full less than an hour.
Again, my problem is more medical than aesthetic so I'm always looking for a grinder that has a long lifespan. Because of how the wheel is set up, you only get a use area of 180 degrees. I like the interchangeable heads on this one. I have another one with changing heads, but they go on and off. This is pretty need with them all in one. I just wish it had a little more power.