The Supreme eGo 900mAh Twist Battery is the standard in rechargeable eGo batteries with variable voltage. Just like the standard eGo battery, the eGo 900mAh Twist also uses a hot button system and includes an automatic shut off for safety. The twist mechanism located at the bottom makes it easy to adjust your volatage from 3.3v to 4.8v. Because of it’s discreet design a lot of people prefer this unit for portability. Simply attach your favorite eGo compatible atomizer, set your desired voltage and start vaping. The Twist Batteries are great for Dry Herbs and Concentrates. charger sold separately