right outside of Maine there are paintball fields and stores that will probably fill co2 if you want to make sure here's the link: http://www.pbnation.com/fieldshow.php?state=me
All Co2/HPA tanks will fit any marker. Co2 cartridges will not.
All Co2 tanks will fit any gun meant to be powered by Co2.
No, they cannot.
The cybrid uses Co2 tanks.
"H" is not a size for CO2 tanks
No co2 tanks are sold full.
They need the small sealed CO2 cartridges, not the screw on tanks. but yes they need Co2 to function.
There are a lot of good sites for co2 tanks. One that I prefer is DicksSportingGoods.com they have a lot to choose from in many different sizes. They also have many other things besides co2 tanks.
Yes they do
There is not a place where you can trade in Co2 tanks. Except possibly a pawn shop.
You can not bring Co2 tanks on a air plane. As it could be used as a explosive, so it would be confiscated when you get checked going through the X-Ray.
co2 tanks are fine for stocks. But if you want more they make caps for the end of the co2 tanks that have a thing like a stocks end. (opsgear.com has em) But as long as the stock outreaches the co2 its good