I have the Topeak RaceRocket. It is 18cm long and mounts on a bracket under my bottle cage. My mini pump is strictly for inflating my tubes for shape and getting the tubes to about 30-40 PSI, then I top it off with my CO2. Of course, the pumps are also my backup option in case my two CO2 cartridges and Genuine Innovations AirChuck Inflator malfunction.