Aerograms is a onion skin like thin sheet of paper that serves as the letter and envelope. Aerograms have the postage value imprinted. As you can see, one can fill 3 parts of the folded inner section with your messages then seal wetting the gummed flaps. I recall purchasing dozens of Aerograms at a time primarily for me and our two sons to write to my Mother.
Enclosures are prohibited but as you can see one can get pretty creative in filling the allocated space. Again with wider usage of email and texts, Aerograms have joined the ranks of dinosaurs. Even for our children this product is as foreign as receiving a telegram.
Aloha -- Cathi