A fuel cartridge includes a fuel tank which stores fuel to be supplied to a fuel cell of a main device, and a storage unit which stores information on type of fuel, remaining amount of fuel in the fuel tank, and number of times the fuel tank has been used. A shaft end of the hollow shaft is bent outwardly in a diametrical direction, thereby being caulked on an outer end surface of the inner ring. A resilient pad is supported on the base and the pad has a top surface, at least a portion of which yieldingly supports a flat substrate placed thereon. Voids are passed through the rear plate and extend axially between the bracket and the sleeve some length into the sleeve. The importance of a system parameter may be weighted over time in an embodiment of the present invention.