The windshields are big, expensive items and very important to keep leak free (especially the rear since the window surround is rust-prone from leaky gaskets). If it's a car you're keeping and MB seals are available, you're a fool to buy anything else, regardless of the cost difference. If you're paying a shop to do the work, you lost any savings if they have to pull the window and redo it because the aftermarket seal didn't fit.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]