These batteries feature variable voltage, allowing you to control how large of a sip you take. With a slim profile and a long-lasting 350 mAh rechargeable battery, this battery can be easily slipped into your pocket or bag for a weekend at the cottage or lounging on the beach. Sold as a display of 12 batteries. Floresense 510 Battery Features: Use: Concentrates 510 Threaded Fits Most 510 Cartridges 3 Heat Settings Variable Voltage Battery 350mAh Battery Capacity Micro-USB Charger Button Activated Display of 12 Batteries What's in the Box: 12x - Floresense Straws 350mAh 510 Battery - Green