If you ordered them from Fastlane they generally are set for the vehicle. I just replaced the plugs in my C280 last night (takes a bow) with Bosch Super's and was cautious in checking each one. They were all fine but I wouldn’t be surprised if they weren’t perfect after possibly getting bumped around in shipping. There have even been reports of them getting bumped out of spec on the way in although if you were careful at all I doubt that would happen. If you’re experiencing a rough idle though I would think it would be worth the time to take them out and check.
1986 190E 186K (For Sale)
(Maroon, Tan leather)
1996 C280 Sport 208K
(Brilliant Silver, Black Leather)
2002 CLK430 Sport 45K
(Brilliant Silver, Gray Leather , Birdseye Maple)