Late yesterday afternoon I was pushing hard to get home before twilight set in. About 12 miles away from my finish I come upon another cyclist who is wrestling with a flat on the rear wheel. I stop to offer assistance. He tells me he has been trying to get the tire with new inner tube pumped up for over 15 minutes without success. He asks if I have a pump as it appears his is not working. I do have a frame pump, but I also carry a Co2 cartridge as a backup. I'm looking at the sun getting closer and closer to the horizon and pull the Co2 out of my jersey pocket. He says, "Oh, I would never use that." I ask why and he responds, "Why carry something like that when you can do it by yourself with a pump?" I look at my watch and say, "Really, how long did you say you've been trying to get back on the road?" He, nods and says, "Point taken." Long story short, 20 seconds later his rear tire is fully inflated and he's saying, "I got to get me one of those." Two minutes later as I'm back on the road headed home I'm thinking that I will make it before twilight and thankful for having the Co2 cartridge with me. (BTW, I've been carrying that same cartridge for almost two years and was starting to wonder why I bother carrying it.)