These beeZbee Cartridge Batteries feature an adjustable voltage between 3.3-4.8v to find the perfect setting for your favorite cartridge. This 900mAh slim twist battery is compatible with 510 thread cartridges in either 0.5ml or 1ml sizes. Each sleek battery is equipped with an automatic 20 second shut-off time and a 2-click preheat mode. A USB Smart Charger is included in each box. Choose from eight colors to match your style: Black Blue Red White Silver Purple Yellow Trichrome Turn your battery on and off with five, rapid clicks. Adjust the voltage by twisting by twisting the bottom.