These units use e-liquid, which is typically flavored and contains varying levels of nicotine. Many people use vape pens as a means to kick their cigarette habit. As e-juice is available with different amounts of nicotine, users can wean themselves off gradually. While all e-juice vaporizers function similarly, things like size, atomizer type, battery life and overall build quality tend to vary from unit to unit. One thing you can expect from every vape pen is a discreet and portable vaporization experience.