Just Batteries VV Twist Vape Pen batteries are a great and stylish way to power up your 510 thread cartridges. Delivering smooth power from 2.5 Volts all the Way up to 4.0 Volts. Which is why this little slim battery isn't shy on power and provides plenty of punch for even the thickest oil carts. Not only delivering big box power in a small / slim unit the battery is 500MAH capacity so you wont have to be attached to a charger during heavy use. Convenience and smart tech is incorporated into this battery by allowing you to dial in on your optimal power setting with the simple twist of the bottom nob and Green, Yellow, red LED light indicator will show you your active battery life so you know when to get to that charger. The battery also has an incorporated advanced preheat functionality to get 510 carts started when they have been sitting or cold weather conditions. Overall in terms of power, convenience, functionality, sleekness and style the Just Battery cannot be beat at the price.