400 - what it came with (325/400)..... his juice is mostly 55/45 or so, so that shouldn't be a problem, right? The wicking/coiling video said 325=pg 400=vg but that they both wick the same - it's more a matter of throat hit - 400 being less. I didn't look to see if there was light through it.....shouldn't be too big a deal or maybe it is, idk- he vapes it watching tv - not like he's running around with it.