I picked up a bunch of those same bags at the ACA convention in New Orleans a couple years ago. John Kuhns from Kansas City was one of the people in the Kordon booth there. If I remember right he also made the remark that if a fish spined the bag that it would seal itself up or you would get very little leakage from it. He also stated that double bagging wasn't necessary because of that. Something I have always done with the standard fish bag. Another thing you talk about the oxygen/co exchange I am also under the impression when you double bag your fish. That exchange is also stopped. If you are interested in or would like to aquire some of these bags, John would probably be more than happy to sell you some. You can get his email address off of the ACA page. http://www.petsforum.com/aca Mike Evans