I was incredibly skeptical about this product.  I have massive calves and wide feet and purchased a pair of knee-high Bed Stus that were incredibly tight in both areas.  The boots would barely zip over my calves (it took a lot of effort to get that zipper up), and the foot portion quickly cut off circulation to my toes upon wearing.

I soaked inside and out with this spray (it took about half the bottle for both boots together) and wore them around the house for under an hour.  Not only did the foot loosen up, the calves stretched probably about an inch in circumference each.  I was pleased to see the next morning that they did not shrink when the spray eventually dried - they kept their new size.

If you have huge calves and struggle with tall boots, try this.  It opened a whole new set of possibilities for me!

One con:  the smell was strong.  It went away quickly with ventilation, but it was pretty potent at first.