Spoke to hellvape this morning. They say it's m3 3.5mm. Tried searching the size and none came up so I'm just going for m3 4mmProbably M3 or M4 and 4mm long. You'll get a pack of dozens for a couple of quid from that plate that does prime. Or you can cannibalise another tank.
Yeah used the spare pack aswell. That's what I get for using there cheap tools that come with it (upgraded now). Spoke to hellvape today and they say it m3 3.5m grub screw I need but none coming up on the searching so just going with m3 3mm grub.Do you still have the spares pack? There should be spare screws in there.