This is a rechargeable 18650 battery (model US18650VTC4 from Sony). It's rated at 2100 mAh.
US18650VTC4 Sony 18650 rechargeable battery cell is made for high current (max 30A) applications. 30 Amps is more than enough to run almost any VV (Variable Voltage) electronic device and is great for mech mods!
It is an excellent choice for people who are looking for quality 18650 battery cells (Personal Vaporizer-Electronic Cigarette, Flashlights, or any application that requires high discharge current).
Charging Lithium based cells: Proper end of charge termination is always required when charging any lithium based rechargeable battery. Charging process should not be unattended.