I was thinking about either the mvp 2 or the vtr. I haven't looked into the vamo too much, but I think I'll have to now! Do you have any thoughts on the mvp 2 or the vtr??
I would recommend the MVP2 as a step up for now.
Consider the VTR in a month or 3, meanwhile you can consider the alternatives.
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Most tubes are designed to take the 18650 size battery; it is 18mm diameter and 65mm long; there are flat tops and button top batteries; some tubes will take one or the other but I think more will take either.
Some tubes optionally take 18350 size battery; 18mm diameter; 35mm long.
My vamo can take an 18650, or I can dismantle one of the lower 2 cylinders and use an 18350 instead; plus I can screw the tube from the bottom onto the top to protect my glass tank; neat.
My Sigelei zmax can't do that; but my zmax is a stainless steel; my vamo seems to be chrome plated brass.
My vamo also has eGo thread, whereas my version of the zmax is 510 only.
Tubes in this class are:
Vamo, Sigelei zmax, smoktech SID, (there is also a Smoktech zmax), Innokin SVD,
theres a new one out called... firestone e-ltc or e-lvt or something.
Higher end tubes are:
Provari, Joyetech EVIC, Innokin VTR, Innokin 134 (I love that beast)
For someone getting into mods, I would advise get something with VW (which turns out to be anything else beside a provari, oddly enough), and look more closely at what goes on top.