I can't watch videos at work. Is it a carto tank? If so, steel tube inside is a cartomizer that has been sold as or user-done prepunched or preslotted so it has 1-2 holes in its metal sidewall. It may need to be prefilled a bit, then inserted through the middle of the tank, the tank is filled with liquid which surrounds the cartomizer and enters through the hole(s) in the carto's sidewall. Then ends of the carto extend above the tank (to add a mouthpiece) and below the tank (to screw into the battery)
If you get everything set up right, it lets you use a cartomizer but not have to add juice nearly as often. It is more suited to someone who only vapes one flavor when out. If someone likes to switch flavors a lot then plain cartomizers are a better choice.
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Somebody who can watch the video can help if that is not what it is. If you mean the tank is "above" rather than around, that may be an Ego-C - dunno - I cannot see it. Got self-appointed bandwidth police here at work.