Mine got vandalized in 1979. The replacement was put in with a black goop that was the consistancy of tar until it set up. The resulting install was sunk into the body too deep and the windshield wipers would not park, hanging up on the stainless steel trim on the bottom. The thickness of the butyl brings it up much closer to where it should be. I have not put the wiper arms yet so I will soon find out if it parks.