Here's what makes the ego twist a twist...

The bottom silver part turns, so you can change the voltage from 3.2 to 4.8
You can see here, it's just past the 4.0v mark (it's actually on 4.2v)
It's not short though - 120mm long - but stocks 1000mAh for your use.
(though power does drop off if you use it at the top voltage)