The PARD Li-Ion 5000MAh, 3.7V 21700 rechargeable battery is designed to be used in select PARD devices. No longer do you have to worry about a dead battery in the field that requires that you go home to charge your device. Now you can simply replace a dead battery on the spot by replacing your dead battery with a fresh one. Carry several batteries in your pack to ensure that you are never left without the Night Vision or Thermal support you have come to depend on. PARD 21700 Battery High Capacity Rechargeable Power for Night Vision and Thermal Accessories