Abstract: A removable cap for closing the filler neck of a fuel tank for an internal combustion engine. The cap includes a one piece gasket and baffle member which not only provides a fluid seal between the cap and the filler neck, but also permits venting of the fuel tank through the gasket. The one piece member includes an annular flat gasket portion integrally formed on the outer periphery of a dome-shaped baffle member projecting downwardly from the inner surface of the cap. Venting is accomplished by means of at least one vent opening extending through the dome-shaped baffle member which in turn communicates via a vent chamber to a passageway formed through the gasket. The passageway in turn communicates with a non-sealing threaded interconnection between the cap and filler neck. A splash guard is also located beneath the baffle member to aid in preventing fuel from splashing through the vent openings in the baffle member.