The empty .5ml Cartridge is a refillable cartridge to use in your O.penVAPE. The refillable cartridge lasts 6 months and can be filled with any herbal oil of your choice. If you're looking for all the pieces you need to mix your own oils, check out the O.penVAPE Kit. It comes with all the essentials, including the O.penVAPE. 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. Note: All sales final on used cartridges. Returns not accepted.