The same thing happened to me. I ordered 2 radiator hoses and a new thermostat. They were at my house in one day, and I did pay for over night shipping. Well actually I didn't pay for any shipping since Fastlane was running that special for orders over $25.
Mike I think the reason you and I got our parts so quick was because "Fastlane" parts come from a supplier here in NJ, Flemington NJ to be exact. When "Fastlane" came on line I noticed that the online catalog was exactly like an outfit called "Megaparts.com". I e-mailed the Mercedesshop guys and they said it was the same supplier. I had in the past ordered from Megaparts and their address is in Flemington NJ. BTW, generally the prices are better going through "Fastlane" vs. Megaparts. For me I benefit from ordering through Fastlane because that way I don't have to pay any salestax, since Mercedesshop in located in Georgia.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member