Good idea in theory
Good idea in theory, but it didn't decrease my metatarsalgia whatsoever.  I used to do a lot of bare foot running and now when I walk it often feels as though there's an invisible pebble I'm stepping on when in my bare feet (it's painful).  Was hoping this device would alleviate some of the pain.  It didn't.  Additionally, the piece feels uncomfortable in the sock and tends to slide a little.  I definitely don't recommend this.  (It does work briefly though, maybe for 20 mins, but then the squishy-ness subsides and you can't tell the difference).
Rating: 2 stars