You definitely need to improve this product -- we spend a lot of money to send sales aides to our customers -- in many cases the envelops came open in route and the contents were lost. We have resulted to using scotch tape to keep envelops sealed.
We use this product to mail out important documents. We used to use the 10X13 lick yourself envelopes but for the mass amounts that we send out we found that the quality of sealing and ease of sealing was better with the pull-and-seal.