You have to know how much moisture is needed to get the flap to stick.
on February 12, 2020
Posted by: Deb
Verified Purchase:Yes
The 9x12" gummed catalog envelopes work just fine. As far as the gummed part you have to know how much moisture is needed to get the flap to stick. I have always use a piece of tape on any catalog envelope be it gummed or self seal. I do it to insure that it arrives safe to our clients.