Abstract: The foregoing and other objects of the invention will be realized by a closure assembly engageable with the filler tube of a fuel tank for preventing the outflow of fuel vapors from the fuel tank during a filling procedure and including a manually grippable generally circular top member having a central axial opening therein for permitting the passage of a fuel delivery nozzle therethrough and receiving a relatively smaller press fitted cap thereat. A threaded bottom member of generally circular cross section extends from the top member for threadable engagement with a threaded opening in the filler tube. The bottom member is of a generally hollow construction and has a central axial opening therein and in which a resilient circular annular fuel vapor absorbent filter element is located.