On the Volkswagen Beetle, Type 3, Karmann Ghia and the VW Thing, there is a rubber between the housing and the engine lid, as well as between the license plate light and the housing.
The rubber between the cover and the housing serves for protection and finishing, the rubber near the lens ensures that no moisture penetrates the light.
Some rubbers are available in two qualities, quality A is equal to the original, while quality B rubber composition and overall finish is of a lower standard. Keep in mind that the life span of B quality rubbers will be much shorter than that of A quality rubbers.
Useful information from Paruzzi magazine and from our YouTube channel :
Look for more technical articles on the page Paruzzi Magazine