The Brass Knuckles Variable Voltage (VV) Battery looks fashionable and sleek, enhancing your vape pen with safe, reliable performance. Choose from two options: Gold 650mAh and Wood 900mAh. Both offer three voltage settings, including 3.2V, 3.7V, 4.1V. The battery is designed to work with concentrated oil cartridges with the standard 510 thread. One button does it all! Click two times for preheat mode, three times for voltage change, and five clicks for on/off action. The LED also changes color based on voltage setting, ensuring that you know what power you are using at any given time.