Put the plastic ones on, as they are all that is available now. I questioned the plastic/metal issue also, but the metal ones wore out so lets give the plastic ones a chance. They fixed the noise in the back of the TE BTW.

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95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K