The current largest single battery mod from the GeekVape Aegis line, the Max100 is sure to please. Using a 21700 battery (not included), you can see up to a ~20% increase in battery life, however GeekVape includes an 18650-battery spacer so you can still use your 18650’s to power it. With the same interface and convenient side lock switch, the Max100 is familiar and easy to use.