I bought something similar from, IIRC, Pro-Bike for under a fiver. It's been used daily for several years and it's about the most useful thing I've purchased for the bike as it fits bottle cages, rucksack pockets, whatever. Love it.What a great idea, if you are not kidding can't visualize a water bottle with a neck big enough to fit an inner tube, will look into it when I'm less tired. Thanks.