I agree with the Volt/Bloog suggestions. I use a Bloog as my out at work device. I wanted something that looked a bit more "normal" for use at work and this does the trick for me. I went with the 102mm auto battery to get the best life out of my battery. Having a device that somewhat resembles a cigarette was something I wanted so I could vape in public without having to play 20 questions every time somebody seen me use it.