Abstract: A composite relatively flexible resilient flap member has a movable flap and is formed of composite reinforcing fibers such as nylon, carbon or polyester impregnated with elastomeric flexible fuel resistant material. A rigid sheet member formed of composite material comprising reinforcing fibers such as glass, carbon, polyester and nylon and epoxy stiffens the flap. The flap overlies a fuel fill opening in a support plate with a major portion of the flap member fixedly overlying the plate. The flap is offset in an opening of a mounting plate secured to the support plate. The stiffened flap member is preformed with a bend to form a resilient biased hinge when flattened, the hinge being spaced from the fuel fill opening. The flap member and rigid member have low inertia to assist in rapid closure. Other embodiments are disclosed. A fuel cell tank breather vent has a tube with a male valve slug having an elongated shank.