WOW!
I got this for Christmas and WOW!  I work in a machine shop and stand in steel toed boots on a concrete floor. This thing feels amazing when I get home. I was a little disappointed because the first one had to be sent back. It worked great the first day, then it just wouldn't come on. Emailed the company and within 2 hours had a response.  Sent a new one with no hassle.  So far the new one is working well. Don't know if this is the problem,  but, I didn't unplug the first one after using like the instructions say to. Will continue to do so with the second one for sure.
Rating: 5 stars