The invention is a piezoelectric modules installed in the rear of the insole. Gravity will produce electricity that passed through resistivity heating modules. It will keep your feet warm in a consistent and safe temperature. As long as you are walking, you will have no cold feet issue anywhere in the world. -Quantity: 1 Pair -Improve cold feet problem -Eco friendly Material and You can cut to customize your shoe size -Piezo-electric energy which power up the heating module. No external Power source needed - Aword winning technology and world wide patent. Additional Details ------------------------------ Package quantity: 1