These are easy to use and do not have to be moistened thereby saving the "yuk" factor of posting assorted mail and bills. As an extra bonus the security lining safely hides any return addresses and/or account information that is better hidden from prying eyes. The paper weight is sufficient to mail several sheets in one envelope without incurring additional postage and the flap overlap allows them all to fit in without resorting to taping the envelope shut and risking taping important papers to the envelope itself.