If I could give these zero stars I would. The adhesive is not very strong and one can peel the flap open even after a day. I have similar envelopes that I bought from Staples two years ago. The adhesive had dried and now will not stick at all. That's why I bought these replacement envelopes which are even worse than the ones I bought before! Looks like if you want REAL security envelopes you have to get the old-fashioned kind.
I really wanted to Buy American but these envelopes had no glue on one side and I had to tape each one closed as I had an 80 piece mailing that had to go out the next morning. I was extremely disappointed in the pitiful quality of these envelopes. How did these even make it out of the factory? Does no one check quality?