I've been pretty fond of the Vivi nova ver 2.5 and the mini vivi nova. Though the mini looks better on a smaller PV like the Ego-c/twist, it's slightly harder to refill since the gap is smaller. If you don't mind a bigger tank, just get the 3ml size. I also like to only fill them about 1/2 way since the juice "cooks" due to the heat, and I don't like to waste juice. Many people seem to fill their tank up, then dump it when it tastes weird at the 1/4 mark.