Originally posted by Dogmama
There are different sizes of CO2 cartridges. What is the size for a road bike?
Many people carry the 12 gram unthreaded. These are usually the cheapest cartridges you can buy.

I prefer the 16 gram threaded. I carry just the nozzle-type CO2 device. I use this size for both the road and mtb.

The CO2 device package will have inflation guidelines on the back (i.e. # of cartidges needed to get to X psi).