I think you might have posted in the wrong section for this question. Typically new vapers want something that feels and/or looks more like an actual cigarette, and will more closely mimic one.
This particular part of the forum is dedicated to what I like to call "hot-rods", or e-cigs on steroids. These in particular are made by Puresmoker and include the Prodigy and Protege. These are extra large battery housings with the ability to enhance vapor produciton, offer much longer vaping sessions between battery changes, and enhance flavor. BUT they do not look or feel like a cigarette. Go grab a screwdriver out of your toolbox and imagine that this is a little more like using a Prodigy... you see what I mean.
Most, but not all new vapers start with something like a 510, 901, etc that more closely resemble the feel of a cigarette. But by no means does that preclude you from jumping straight into the deep end! If you don't care, or have a need for a unit that looks/feels like a cigarette, you can't do better than a Protege or Prodigy. The Protege is a smaller unit that vapes at 3.7v for a wallop of vapor and flavor and a cool sensation in the vapor. The Prodigy on the other hand is much larger and vapes at 5v and provides INTENSE flavor, BILLOWS of vapor, and a slightly warm sensation to the vapor.
Here is a photo I took with several types of e-cigs alongside my Prodigy and Silver Bullet mods:
In the foreground you'll see my black 510. Also in there (red and blue) are SideSho, and the little tiny guy is a Blu. On top of the skull is an M401 Dragon. Hopefully that will put the sizes in perspective for you.
