The A Team of Envelopes
"A" size envelopes. A-envelopes are typically used for more formal communications such as invitations. They are made from thicker paper stock and usually come in a wider variety of colors and finish than some of the other envelope sizes. Most A-envelopes also have side seams (the back of the envelope is put together with two vertical glue seams as opposed to three triangular flaps) which give a more finished look to the envelope.