About 1 1/2 inches of each envelope is sealed on one side which is really inconvenient. You need to "open" the envelope in order to fill it and that side gets messy and doesn't seal again. Doing that with 500 envelopes will not be easy. I'm sure I just got a faulty box but still...
They are solid envelopes that don't come apart on the sides like others that I have used in the past. They are secure as you can't see the writing on the document through the envelopes. I will get these again. I would recommend these envelopes.