What Kent said (forgot the "t" in his name in my earlier post). He is usually right on when it comes to product evaluation etc. and explains it from a material and processing point of veiw. I'll follow up with a practical and common sense point of view. Take a look at the whitewater industry (Sotar, Maravia, NRS etc.). None of the leading pontoon makers use a bladder system with a zipper shell. Aire used to in their most economical pontoons. Not sure anymore. Think about zippers and all the things that can go wrong with them. They break, get debris in causing difficult zipping etc, you overinflate which can cause stretching on the zippers. The high quality bladderless pontoons are much more resistant to changes in temperature and altitude although you still need to be careful. Years ago when Scadden first came out and was doing the outdoor shows and selling pontoon boats rather than his new U-boat design, he offered bladderless and zippered boats. The bladderless boats were substantially more, say in the $500 to $600 range more. That is because they are better boats because the material is better and cost more to make. There is a reason why all the economical pontoon boats sold at the big box stores are in the hundreds of dollars and regularly go through changes every few years where as the high quality whitewater pontoons are sometimes in the thousands of dollars and bascially remain unchanged year after year. The materials and design are much better. Recently I sold some tubes to Jeff Bandy, fellow WFF. He posted about it on the main forum. One comment he shared with me was his experience with the bladder and shell pontoons he had before and the fact that the valve opening was often difficult to find and air up because it somtimes became diffucult to line up both valve openings. The valves in Maxxon tubes are better and can be replaced if needed. Not sure about the cloth shell and bladder pontoons. Another issue is the bladder can become scrunched or squished at the tips inside the outer shell thereby not fully inflating and causing you to pull them out of the cover to take out the blockage. There is a market for low and high quality boats just like everything else.