The Ooze Slim Pen Twist is a 510-thread variable voltage battery with a twist dial at the base for adjustable power (3.3V-4.8V). 320mAh rechargeable lithium battery with USB charger included. Slim, pen-style design fits discreetly in any pocket. Compatible with all standard 510 cartridges. Available in Black, Chrome, Rainbow, Gold, and more. One of the best-selling 510 batteries in the market.