Another option in the mini catagory..........I have had no trouble with the Volt I just got. It is small and looks like a cig, but it has been trouble free. I also put the cartomizer on my thermo tube with a 3.7 via an adapter, and the battery lasts 2 days. Cartos are easy to fill/refill and give good flavor and warm vapor for a regular resistance and 3.7. I was using mods all the time, and was surprised to find this one becoming my all day unit.