After finding and putting batteries into these socks I put them on and turned them on. Initially t felt as if there was cardboard under the front half of my feet but I soon forgot about it. It heated up within a minute. I only really felt heat on the front half of my foot - not by the heel or all around. But, the toes are what I’m worried about for frostbite. The heat wasn’t extreme - you could wear this for hours (not sure how long the batteries will last). The true test will be when it’s sub zero and hubby uses them for shoveling snow.