Ooze Twist Slim Pen
The Slim Twist Pen features a dial on the bottom that twists to select a precise voltage between 3.3-4.8V. Press the button down to take a hit, and the battery will shut off after 15 seconds of inhaling to protect against overheating. Activate preheat mode by clicking the button twice and the battery will heat for 15 seconds without needing to press the button down.
This is a 320 mAh device that includes an Ooze smart USB charger with built-in overcharge protection. The charger automatically shuts off as soon as the battery reaches a full charge, greatly extending the overall life of the battery.