I was on a group ride a few weeks ago where another cyclist flatted and used CO2 to fill the spare tube. Of course the moron left the cartridge laying on the side of the road as he took off. I came back and picked it up. I just don't get it, those things weigh nothing and the dude was already were carrying it, why on earth would he leave it on the side of the road after he used it? Pick your crap up!!!