I keep the Portland Design Works "Shiny Object" in my seat bag. It takes very little space and is reliable. It has the on-off valve to control the flow. I've used it on the side of the road during my commute and it worked flawlessly. Just be sure to practice once in the garage. The key for me is to remember that the valve must be in the closed position when screwing-on the CO2 cartridge.

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