I think the unit could be a bit more powerful.
During the pandemic, my feet got incredibly rough.  I spent more time walking barefoot around the house, and my pedicurist was closed for months.  I decided to trying doing my own pedicure.  I think this Wonder 4 will do a nice job, but it is taking some "getting used to."  I had to experiment with the different grinding heads to determine which worked best on my feet.  I think the unit could be a bit more powerful.  But, it does smooth rather quietly.  It just takes a little longer than I expected to receive "professional-like" results.  The rechargeable battery makes it very convenient.  It is supposedly for wet or dry use, but I have only tried it dry.  I feel that smoothing would take even longer if I added moisture.
Rating: 4 stars