That's not the correct part number. I have that and it definitely will NOT fit the reservoir of my 420 SEL.

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I'm wanted in four states, but it's all good. Got me a new driver's license and a sweet new pickup. V-8, Baby, five-hundred horsepower. Oh, and four of them mudflaps with the naked ladies on them. GRRRRRRRR, MAMASITA!!! And the best part is, it's all free!!! Yeah, well, for me at least!!!! HA-HA-HA-HA-HA!!!!