The Hotronic S4+ Footwarmers are the advanced way to stay warm in the elements! The Foot Warmer Power Plus CUSTOM comes with 2 Battery Packs, 1 Recharger, and 1 pair of Heating Elements with Cambrelle® Covers. For use in HOTRONIC's Heat Ready Insoles or on custom insoles, orthotics, or insoles of one's own choice.