There envelopes are well made are much stronger than the standard envelopes and have a better stronger sealing flap. The paper of construction is heavier and darker than the standard envelope for excellent privacy and security.
I have purchased regular envelopes in the past which you lick to seal. In the summer these cheap envelopes stick together. Is there a regular envelope which is better quality and does not stick in the basement. I find the recent ones I bought somewhat exspensive.