This is a private label battery with a USB charger, stylus for your electronic devices, button for variable temperatures, 5-10 universal thread and fits any universal cartridge. We only sell universal, 5-10 threaded cartridges, so this will accommodate any cartridge on our menu. These have a 30-day warranty. These normally retail for $30-$40 from vape pen companies, but we sell them black labeled for only $14.95. We also give them away for FREE in some of our combo packages in our DEALS section of our website, or you can also get one for FREE when you order (3) or more cartridges. Instructions: Change from 3.2 volts to 3.8 volts to 4.2 volts easily! Simply click the on/off button, also known as the fire button, five times and the Black Label 2.0 battery will change the voltage and let you know the voltage by the color ring around the button. RED means that the voltage is set at 3.2 volts RED and BLUE (kind of looks purple) means that the voltage is set at 3.8 volts BLUE means that the voltage is set at 4.2 volts To use, simply hold the button down while inhaling (after holding button for 10 seconds, LED light flashes 8 times then the battery automatically shuts off). **Most cartridges should not be used with more than 3.8 volts.