These enelopes are a staple (pun intended) in my office. I don't use these envelopes just for mailing letters. They are the perfect size to hold credit card receipts so that the entries on the credit card bills can be verified. I also use these envelopes to write my shopping lists on and the coupons I want to use can be secure in the envelope till time to check out.
I have used these envelopes for years. One problem - the gummed flap semi-seals after going through the laser printer and I have to pry them open to put the letter inside.