I purchased the same part for the right rear door window on my 1992 190E at a local Mercedes-Benz dealership. The new part looked similar to the old one, but I couldn't see how it fastened to the cable. The parts girl was clueless. With both the old and new parts in hand, I asked a service writer to explain how the new regulator guide jaw fastened to the cable. After he talked with numerous mechanics and the parts manager, they determined that there's no way it can fasten to the cable. It is not a revised or superceded part, it is the wrong part. The correct part is not available. They said you have to buy the complete regulator assembly.

After looking online at many pictures of regulator assemblles for different models of Mercedes, this part is probably for the front door regulator only, as the cable style regulator is used only on the rear doors. The part descriptions shown by all of the online parts vendors that I could find, including Fastlane are not clear as to which door this part fits or doesn't fit. They just show a regulator guide jaw for most models, which makes one think the part fits all four windows. The pictures they are showing of this part are identical to the part Mercedes tried to sell me.

Even if one had the same model/series parts car to cannibalize the part from, it's about impossible to remove the guide jaw from the metal track that it rides on without breaking the small grooved tab that holds it on the track. If one was lucky enough to get it off intact, they'd probably break it when putting it back on. This part is very brittle and is designed to fail. I'll add this one to my long list of automovtive scam designs where some 5 dollar part fails and you have to buy a complete assembly priced between $170 and $300 to fix the problem.