VW calls this a grommet, but it's actually a hollow tube that the washer fluid hose runs through between the body and rear hatch on the passenger side of the hatch.  If needed, here is the Rear...

Driver/Left side. JP Group brand. It has always been the case that the best way to install these is to determine roughly where the mirror positioning should be before attaching to the van and then...

Excellent quality rear hatch seal for your 1980-1991 Vanagon.  Profiled just like the original for a perfect fit.   Ref ID: 255829193