for a 1995 e320, the old radiator fitting decided to relieve its presence from my radiator in an very Old Faithful kinda way. in any case, I've got a new one but in the little baggy was an extra o-ring. I know that there is supposed to be one on the body the fitting (which is there) but what to do with this other one? extra? I'm hesitant to snap in the fitting since its pretty much a one-way deal and then realize that this second o-ring was critical. what say you? packing mistake?