Bought a "Health-e-Cigarette (M-401) first. Big mistake. Bought a 901 kit 2 days later and that was good for a month until I got sick of charging batteries. Bought a 905 mod that was a piece of crap so I started to make my own battery mods. I bought a Chuck without a finish so I could dress it up with a wooden veneer (I'm a woodworker) and recently bought a Riva just to see what the eGo, Riva, Tornado thing was all about. I use 901 HV attys, 510 HV attys, 510 LR attys, kr808D-1 cartos and 510 cartos. Yeah, I use them all from time to time depending on what device I pick up and what mood I'm in.