Toe Heaters II simply 'run on air'. Just open the package and expose the Warmer to air - the reaction begins immediately. Designed with adhesive backing so they stay exactly where you put them. Simply stick the Toe Heater II to the outside of your sock, slip your foot into your boot or shoe and enjoy Six Long Hours of nice warm feet. Maximum temperature in shoes 100 F. Ideal for skiing, hunting fishing, camping or working in cold weather. Odorless, non-toxic, bio-degradable and disposable.