The Ooze Duet is a unique 510 thread battery that features double 510 threads, so 2 cartridges can be used at once. The IntelliSwitch controls if the left thread, right thread, or both threads are activated. The Duet features a digital screen with a battery indicator and voltage level, and completely conceals the cartridges inside. It is compatible with 0.5g and most 1g cartridges. It does NOT include a charger.