• Heat duration: 4 - 8 hours • High performance rechargeable Li-Ion battery packs 3.7V / 2.4Ah / 8.9Wh (BP18) • Battery Pack: Small, light (64g) and compact (55 x 86 x 11mm) • Battery pack with remote control • 3 heat settings • 4 sizes: • Small 36-38 • Medium 39-41 • Large 42-45 • XLarge 46-48 • Carbon thread heating element under the toes • Pocket for battery pack on the top of the sock • USB charging cable • Charging time: 4 hours