sealing strip doesn't hold to edge and corners get caught in the postal systems machines so cards get damaged. Need to add a strip of clear tape to hold it down defeating the self seal feature.
I've seen these types of flap seals come undone through mail handling so I end up adding a piece of tape to the flap for insurance. So there goes the efficiency. It's obvious they don't stick as well as the old lick 'n stick.
The only reason I did not give it 5 stars is because I wish it came in a smaller quantity box. A bit pricey for my current needs (invites for a birthday party) but will eventually use them all between invites and home made greeting cards. Appreciate quick strip and not needing to lick all of that yucky glue!