The part of the lid was very hard, it was hard to open and it was serious. So, there was a case where there was only halfway in the time of fitting. But it is safe to say that people who are firmly engaged are not worried about being out during transportation.
I purchased it for poster sending. Because the lid is sealed on the outside, it is easy to paste gum tape for preventing water leakage. There is concern that water penetration does not exist because paper quality is slightly coarse.