rear marker lights, left dimmer than right?

[co_g30]

Greetings

new owner of a 2005 X5, loving it so far.

question though....in the tailights, the middle lights which are the marker lights....the left side is dimmer than the corresponding light on the right side when the lights on.

Not talking about the lowest set of lights, the tail lights...those are the same.

Just wondering why the light bulb on the left side assembly is different (two filaments) vs the single filament bulb in the middle of the taillight assembly on the right.

The left side bulb emits a much weaker light that the right side....

tia

dom