Description The Hotronics S4+ Custom Boot Heaters provide a stronger and longer-lasting heating system that keeps your feet comfortable. The Battery inside the Hotronic's S4+ Custom Heaters lasts up to 21 hours and the heater itself features 4 different heat settings.   Includes 2 battery packs Charger Heating elements Cambrelle Covers European Outlet Heating Chart Hotronics S4+ Custom Boot Heaters