The Mini Cig
Also called 'slim' e cigs, these are the units with the smallest batteries. They are designed to resemble the size and look of a traditional tobacco cigarette, as well as the 'drag to activate' mechanic that current smokers are already accustomed to. In fact, nearly all automatic batteries are found on this type of cigarette. The combination of these qualities makes mini cigs the unit of choice of most new vapers. The downside is that, with a smaller battery, they need to be recharged more often, and usually require a portable charging case to keep them going if you plan on going out all day or night.
The Fat Battery Cig
By far the most popular among average vapers, it is best known for the tank models. As the name would imply, they sport a larger battery which can hold a bigger charge and last longer before all power in the battery is drained. The vast majority of batteries in these types of e cigarettes are manual, and automatic models that work with a vacuum sensor are extremely rare. E cigs of this kind also run at higher voltages than mini cigs, providing additional throat hit and thicker vapor.
The Battery Mods
The device of choice for expert vapers, a battery mod is essentially a tubular casing that can house many different types of special batteries. Some of these battery mods can run at higher voltages than fat battery e cigs, but the most popular units in this category are variable voltage devices. Variable voltage means that a user can customize the electric current fed to the atomizer, allowing vapers to find their own 'sweet spot' based on their atomizers and specific e-liquid. In a nutshell, voltage alters how hot the atomizer coil gets and how quickly; and this in turn affects the strength of the throat hit, the vapor production and the taste of the nicotine fluid. Too little voltage and the device gives a very anemic vaping experience; too much and it will give a dry, scratchy and harsh throat hit with a nasty burnt flavor.
The Box Mods
Like the standard tube mods, box mods are a casing for special batteries. Besides the obvious difference in shape, box mods are often altered into so-called 'juice box' mods, which can hold a bottle of e-liquid to automatically feed nicotine fluid into the atomizer. Just as with the other mods above, they also come in variable voltage versions.
Less common and usually much more expensive, e-pipes are the luxury item of electronic cigarettes. These are usually manufactured similarly to a battery mod, but the casing is a beautifully hand-carved wooden pipe. Cheaper versions of e-pipes that sell for 50 to 60 do exist, but these are usually lower quality, use a plastic pipe or have some other problems.