This “support single 26650, 18650, 20700 and 21700 battery.” caught my eye as well and thought cool! I was interested more about it so i checked out your site for more info @3avape. This brought more questions. The site only states 18650 and 26650 and shows an adapter for 18650 to take up the slack. Now got me to think there were really strong springs to take up the extra length but thks to @Sprkslfly, i know now that the adapter for 21,20 series is optional but available. Your site advertises a usb cable is included which seems to be either false or useless, as there is no usb port on the thing,unless iam blind. So, I believe your site and the advertisement here needs a lil tweaking. Sry for the slight derail but anyone looking to invest in one would appreciate as much info as possible. GL to all!!