Abstract: Embodiments are directed to fiber-reinforced compressed gas storage tanks or vessels comprising one or more shells that are made by metal forming, plastic molding, braiding, filament-winding, or fiber placement. Particular embodiments employ one or more discrete pre-formed fiber-reinforced endcaps with fibers oriented in preferential angles that are integrated to the vessel end-domes to reinforce the polar openings and the dome-cylinder transition areas of the load carrying shells.