CO2 inflators

Just did a test to see whether I should carry one or two cylinders.

Each one added about 70 psi to a 700x25c tire. So, one will get you home, but two is what you want if you want to keep riding with normal pace and effort. And you need a gauge or you will be riding with 140 psi in your tire, or you'll be guessing at how much air to let out.