I have yet to use a padded envelope. I use the standard manilla (brown paper) envelopes that have a metal clasp on them. And I usually send the flies in the same clear front case I plan on displaying them in. I just stuff that and the return envelope into the bigger one. Is this risky? Sure, but I can't afford to spend a small fortune on postage year-round. Also, If the person lives on the other side of the country or it's getting close to deadline, I'll spring for priority mail. Sending stuff to John R in Knoxville from NE Nevada, I have priority going both ways. I also tape all the seams on the envelope. I always look at it as the flies I get are worth more than the postage.