that I can keep in my camelbak for adapting a petrol station air line to fit a Presta valve? If I'm out and I get a puncture I tend to be able to get enough air into the fixed tube to get me home or back to the car (gently), but nowhere near enough for hard/rugged riding. If I could stop at a service station and top up the air to a rideable pressure I could keep riding. . . .