What size Reccomended(spel?)

Well am long gone from not being able to grow my VFTs and now they are large with big red mouths which is awesome. I am fixing to order 5 Red Dragons (bareroot) from a different website and I needed help. What size of plastic pot would be good for 5 of these full grown?? They aren't going to be full grown when they get here but I am looking ahead for the future. I know I need a deep one which I will get I just don't know what size like how many inches or so or whatever. So can anyone help me???
Tut tut, buying from another site eh?

Well, the depth won't change, so the depth of the pot should be at least 4". Then I would give each plant a 3" diameter as Red Dragons tend to grow more upwards.