There are several different things that people refer to as tanks.
There are Stardust/Clearomizertanks....
GotVapes VISION eGo Stardust 808 1.6ml Carto 2.5-2.8 ohm CLEAR [gv-visionstardust808-2.5] - $4.95 : GotVapes.com, E-cigarette Supplies - Atomizers Cartomizers Mods Juice and more
These are most often used by people who have some sort of eGo battery. They have a wick in them that absorbs the juice and wicks the juice to the atty in the bottom of the tank. These have to be trashed after awhile.
There are Vivi Nova tanks......
Vision Vivi Nova Tank System
These are used by alot of people, on various devices. The heads are replaceable.
There are carto/tanks.......
6ml Glass Tank With Chrome Metal END CAPS!
Alot of people use these also. They can be made of either a plastic tubing, glass tubing, or stainless steel tubing. The end caps can be made of either delrin, rubber grommets, or stainless steel. On these, you replace the cartomizer only.
Then there are atty/tanks....
Reactor
These use an atty that has holes in it. This is a relatively new setup, and I'm hopeful more types will be available soon. Again, on these you replace the atty, and not the whole tank.
Those are the basic types of tanks available. I'm sure I probably missed something....but I'm equally sure someone else will come along and point that out to me.
The above links were provided as a picture reference only. (I sound like an advertisement here

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I'm not saying though that those are the tanks that I recommend or use myself...just to give you an idea of what's out there.
Hope this makes everything as clear as mud for you!
