Portland Design Works CO2 20 Count Box lets you stock up on cartridges so you don't have to waste time constantly re-upping your CO2 stash. The 16-gram, threaded CO2 cartridges are compatible with most inflators and fit easily into your jersey pocket or seat bag. And you don't have to worry about any freezing ooze ruining your inflator or valve stems because Portland Design Works' cartridges run clean.