Been wondering this about CO2 cartridges...
Does one cartridge fill up an entire tube? Road and MTB?
And if you just need to top off your air pressure, can you use CO2? Or is it a one-shot deal sort of thing...once you've punctured the cartridge, do you have to use it all at once?

Hate my teenytiny pump...very ineffective and it doesn't fit in my under-saddle pack, so I have have it strapped on the bottom of the pack with thick rubberbands...hehe ugly but it works. Don't like to carry things in my jersey pocket other than yummies and route sheets!