I currently have 4 MM bags. With all the fish I've purchased from different vendors I've only liked how a few packaged the fish. A lot of boxes come in very wet, that tells me the bag was punctured and when the box is opened, that exactly what it was. This last one was even wrapped with duct tape, if the plastic is compromised, it will leak, duct tape or not, unless you wrap it so many times, etc but that adds weight. I just sent a test box to FedEx using two 4 MM bags each for the bag of water and then the liner is also 4 MM, I'll know the results in about a week.