Before I replace this water pump on my 2003 E320, why are there two water pump gaskets? One is flat and is the exact configuration of the water pump while the other one included in the box is a rubber style which is "tubular" like an o-ring. Why do they supply two? What application takes the rubber one?

Easiest way is to remove the water pump on the car, and use the same style that was on there. Since both are in the box you can't really loose.

Right... I figured that much. I was more concerned that maybe the original gasket from 2003 has been superseded to a dual replacement gasket - as an improvement. I imagine that the rubber gasket is for a different engine that uses this same pump.