LOL I didn't know how they worked. I thought it was like a Styrofoam chest, put something warm in it and it stays warm, put something cold and it stays cold. Thank you for the information.If you heated it in your microwave if it didn't ruin it, it wouldn't stay heated long enough. Heat packs all you do is expose them to air and they automatically warm up and stay warm for as long as they are suppose to. I found a heat pack so I don't need one anymore.
