I love these envelopes and have been using them since I retired. Just remove the strip and close without having to lick it or use a sponge. They stay closed.
I often have to send out large mailings -- 40 to 50 -- to members of my organization. While I am seldom mailing sensitive materials it is often important that those materials absolutely get to the membership. I found that working with old fashioned envelopes it was sometimes difficult to get them to seal properly. Plus it has a hassle either licking them or using one of those bottle-things to seal them. These envelopes make the whole process faster. I am always sure that the envelop sealed. No extra double-checking before mailing.