A small enough bag to fit under your seat without scraping your thighs, yet large enough to hold two 700C tubes, two CO2 cartridges, and an inflator. What's the point of having two spare tubes?  You never know what lies ahead, so it's nice to be prepared. By having an extra tube with you, you won't have to make calls if another flat occurs, so it will make the rest of your ride better.

Black Canvas with Piping in: Black, Blue, Gray, Pink, Red, White, or Yellow