The Happy Stick premium battery and case provides convenient storage and power. With its multiple voltage settings, this premium battery offers three different levels of intensity. To use the Happy Stick: 1. Press the button 5 times to turn the battery on and off. 2. Press the button 2 times to pre-heat the coils. This will prolong coil as well as help on cold days. 3. Press the button 3 times to change the power level Green = 3.6 Volts, Blue = 3.8 Volts, Red = 4.0 Volts Like all our pens, the Happy Stick comes with a lifetime warranty. *We do not sell pre-filled cartridges online. This listed product is the Happy Stick battery & charger. If you would like to purchase pre-filled cartridges for your HappyStick, please see our list of distributors. This product is intended for use with essential oils and herbal extracts in states where the sale and consumption of such oils and extracts are legal.