Do you want to learn A7 envelope size? Well, Here is it. No matter why you are asking for it here is the answer.
When things getting important, Envelope sizes start getting bigger as a result. When you open your mailbox ( real one which stands in front of your house ) if you find huge Envelopes. You can understand that you have some important news ( good or bad - mostly bad. No one sends good news via letter )
A7 envelope size bigger than a2 envelope size.