These things work as expected. The intent is to keep your feet at body temperature. I just used these over the weekend on days where the temperature was ZERO... they worked. I like the fact there are no wires (I have ski boot heaters with wires and BIG batteries). The smartest way to use these insoles is to put them on medium to get the maximum time.
I have used these foot warmers many times, so this is a repeat purchase for me. My feet used to get so cold that they hurt when I was out in cold weather or snow. Insulated boots and wool socks did nothing for my frozen toes. These foot warmers are little lifesavers. They stay warm about 5 hours, so if you're going to be out longer than that, take an extra pair. The only downside, I guess, is that they're disposable, but if I have to choose between going green and having frostbite, it's no contest. I've tried the battery operated socks, but I haven't found any that are comfortable and/or durable. (Don't get the disposable toe warmers; they're worthless.)
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