It's a missprint. There is no v3.0
v1- long wicks, airholes in the cylinder metal base under the
tank. Faulty heads that burn rubber base.
tank not
juice resistant. Center pin to long.
v2- short wick, airholes in the center pin. Problems with leak between heads and cap
v2.5 Long wicks, airholes in the center pin. All issues resolved and a great vape
Luckily the v2.5 heads can be used in the previous versions, but may leak at the cap due to them being a spot shorter. The solve is to put a stardust condemn on the head which is a bit longer and resolves this issue.
Also most sites mistakenly list the tank as a 5ml tank. It is NOT a 5ml tank, you can only fill it to about 2.8ml