Perfect for using for kit inside your hull zip storage - simply pack seal insert and inflate for a snug fit in you tubes: with the additional benefit of 25l of floatation per tube! Also, great as a daysack / overnight sack liner drybag with multiple uses.  The TPU dry bag stays airtight once sealed and the ingenious valve at the bottom allows for air to be blown in - to ensure floatation - or sucked out to pack small.  Absolutely bombproof design too - Jason's has been using and abusing his for over a year now with no leaks or issues - from guiding trips to improvised wilderness first aid splints- see pics!