ThermaPet Cat Mats are made with metallized polyethylene terephthalate (MPET), the same material used in space blankets. Originally deveoped by NASA for the US space program, MPET is scientifically designed to offer maximum warmth without weight, bulk, or the use of electricity. MPET in ThermaPet technology utilizes passive reflective heat transfer, keeping pets warm by reflecting back their own body heat.