Everything i've read on this forum about that stuff says its to stop the from chafing and squeaking against the windshield.

As far as replacing it, there's a thread on here somewhere where a guy with an 87 300d actually had his wife sew on some sort of piece of cloth she had in her sewing kit.

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Streetside: 1987 Mercedes 300E Petrol Blue/Green
2014 Ford Mustang Grabber Blue
1999 Ford Ranger Green

Dockside: 1968 Eltro 17
1985 Silverton 34C