These boots keep my feet very warm and the heaters are great. The first 2 times I used them in Jackson Hole the built in J-bars in the heels squeezed and rubbed on my heels so bad I had bruises and raw skin. I had to rent boots for the rest of the trip. When I got home, I put softballs in the heels and tightened the laces to flatten out the J-bars. Now they fit great. The J-bars barely bother me and my heel stays in the boot nicely. I almost gave up on these boots but now I love them. If you buy them, make sure you wear them around the house and break them in first.