Interior (underfoot) is a foam incorporated the is unable to attend it as warm. But I've taken out.
Very little feet have here perhaps problems - can not imagine that here the feet are really warm me. I have shoe size. 40/41 and have no problems.
On the downside, the heating effect could be stronger.
I use the foot warmer at the highest level - Level 1 and 2 are not to be used.
For my purposes it is sufficient anyway. I would give it 3 1/2 stars here.
