The clear tanks that are common these days are made from PETG plastic just like most clear plastic beverage bottles. It is cheapest to buy this kind of tank as an assembly rather than gathering the various parts and assembling your own. Tanks are available from many vendors such as Extreme Flight, Valley View RC, various Chinese vendors under the Kuza brand and others, etc. Many outlets and most are made by Kuza. I'd always recommend a 3 line tank in a gasser.
With the right stopper and fuel lines, Polyethylene tanks like DuBro and Sullivan are still viable for gasoline and are still widely used.
I usually use something like a 12 - 14oz tank on a 20 but sometimes I fly these planes longer than is usual so 12 would be more than plenty for most applications. You would use a larger tank in something like a warbird where you are flying at full throttle more than in something like an aerobatic plane where you use the throttle more.
Last edited by Truckracer; 02-01-2021 at 08:42 PM.