There are two choices for the rear seal. One is just like the original, the other is called a repair seal. The repair seal is dimensioned slightly different so that the lip of the seal does not contact the crank surface in the same place as the original. If the original seal wore a groove in the crank sealing surface, and you replace it with an original seal, it is likely to leak also.

J. M. van Swaay

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1994 E320 Wagon, 230,000 miles
1995 E320 Sedan, 106,000 miles
1994 E500 Sedan, 79,000 miles