This's what makes them really easy to use: all you have to do is top off the cartridge, screw on the end, and puff away. You can select from disposable, reusable, as well as refillable varieties of vape pens, according to your personal preference. The refillable and reusable pens are going to save you money in the long run as they will merely need to be exchanged when the cartridge runs out....