They are not OEM. That was likely Bosch brand. the one Nissens brand I have seen did have the reinforced upper neck so in that regard may have been better.

Use only MB coolant and the plastic parts seem to last longer.

If there is ANY possibility that coolant leak will become serious I would change out the radiator completely.... overheating can ruin the entire motor and break the Bank $$Money for maintence is never wasted, since MB motors will outlast the entire car if cared for well and oil/filter changed regularly.
DanielW