Avg ML is 4.5 - some minor variations.
Nano kit - Reduces Height / Reduces Volume, maybe 2-2.5ml. Nano is removing the largest storage area of the tank - the upper area.
Does not fit ALL models - verify
fasttech Hybrid adapter is 3.1 only replacing the Catch base
PMMA for Look, if you like it - Do NOT use with tank crackers, some are very strong and will win. Metal tank only recommended.
fasttech Kayfuns - Most are good - Read forum review on each.
$14 Kayfun lite - not a 1:1 clone but looks correct externally and Vapes very good. Hey, it's only $14
Even the Cheapo Rocket Tank (ClownFun - lol) is a Great
vaping machine @ $13. Even has AFC