I have wanted to build a 5V tube style mod, but could never come up with the right length of tube to handle the batteries and still leave room for a chip and switch. Last week I realized that a $1 flashlight from Dollar Tree will fit snugly inside of one from Home Depot. The next one will be painted and have a switch more to my liking before going together, but this one gives a good idea of the way they fit together. The batteries take up the whole black portion and the on/off switch is retained. The silver portion houses the atomizer, regulator and switch and is then inserted into the black one. It makes for a pretty simple and cheap 5V device. Less than $20 including batteries. Hope this is useful to someone thinking the way I was.
