The concentrate oil cartridges are compatible with the Brass Knuckles 900mAh Adjustable Batteries. The 900mAh battery capacity, variable voltage, and preheat mode of the Brass Knuckles vape pen make it an excellent choice. It functions similarly to a standard vape pen battery, down to its single-button interface.

If you press the power button for 5 seconds, the battery will turn on or off; if you press it for 2 seconds, the preheat mode will be activated for 10 seconds; if you press it for 3 seconds, you’ll be able to adjust the voltage; the LED light’s color will change depending on the voltage you choose. The voltages are as follows: 2.4V (green), 3.2V (blue), and 4.0V (red).