Mud Flap Installation Grommet These are the plastic grommets that go in the holes where the stock mudflap mounts to the body of the Vanagon. You will see two holes drilled into the body of the van. These holes are much bigger than the metal studs that stick out of the mud flap. This hole is meant to be filled with this plastic grommet. This allows the metal stud to be firmly in the side of the van and also prevents water from getting in the hole. You will need 2 of these grommets per mud flap. If you have a set of four mud flaps you will need 8.