Fuel filler neck grommet.
Dimensions: 70mm outside diameter, 56mm inside diameter.
Fits: 1980-83 Vanagon - typically aircooled and diesel with steel filler neck.
Have a plastic filler neck? Get the 251-201-139A grommet.
On install, be sure the inner lip is in place by feeling around the seal. You may feel a bump or small distortion meaning the grommet is not seated properly and needs adjusting.