I go for the cheapest - at least I think they are.
The 'invitation envelopes' are - perfect for 4x6 photos. 4 3/4 x 6 1/2 in. Fifty per box.
The 'greeting card envelopes' are 5 3/4 x 8 3/4 in. Fifty per box.
Five dollars each @ Walmart. They have recently stocked up on a different and cheaper brand - these run about $3.49 each. Not sure how many are in a box though.

[img]http://i1242.photobucket.com/albums/gg529/stantzspengler/Autographs/6.png[/img]

You can buy your envelopes from a post office or any drug stores or even staples, office depot, etc.,

So were do you guys buy your envelops? Ive only seen them sold in packs of 25 for about $5-8 ..