20ml is a perfect size to try out a flavor. These e-juice bottles are very common and are small and portable. It’s convenient for trying new flavors with these 20ml bottles as well as they last for almost a week if used for moderate to low vaping. It gives you the chance to save some cash while being able to try new flavors around. So with these 20ml bottles you can easily try a flavor before ordering online or committing to larger bottles.