Depends what sort of wattage and where you would predominantly using it really, if using out and about then you will probably want something smaller with single battery preferably 21700, if for at home then probably something like a dual 18650 but again depends what you're sticking on top of it really and running at, dovpo topsides are great squonkers duals are quite big and heavy, where you can still get the single with a 21700 battery, although still quite heavy, other options are as
@rew said the pulse 2, there's the wotofo profile squonker although only a single 18650 but can be got for pretty cheap, lost vape have just released a new one the quest centaurus which is a single 21700, there are a few others on the market
I run the single topside on a 21700 battery and a lost vape drone with dual batteries both with a profile mesh rdta in rda mode normally around 60-65w, depends what your planning to use on top, single or double coil RDA, mesh etc
Hope that helps, probably best to not spend a load of money, maybe try it out first as squonking doesn't suit everyone but its what I generally use at home
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