[double_n01]

i honestly have no clue why there is a mailbox in this bumper? anybody know?

[EastCoast335i]

Its a rear difusser...
Probably more cosmetic then functional on our cars... But in true applications it does serve a purpose:
Source Wikipedia:
A diffuser, in an automotive context, is usually a shaped section of the car underbody which improves the car's automotive aerodynamics properties by enhancing the transition between the high-velocity airflow underneath the car and the much slower freestream airflow of the ambient atmosphere. It works by providing a space for the underbody airflow to decelerate and expand so that the boundary between the car's airflow and "external" airflow is less turbulent, and it also provides a degree of "wake infill" (the wake being a turbulent area of low pressure that is caused by the passage of the vehicle through the air; this can cause pressure drag).
As the air enters towards the front of the car it accelerates and reduces pressure. There is a second suction peak at the transition of the flat bottom and diffuser. The diffuser then eases this "high velocity" air back to normal velocity and also helps fill in the area behind the car making the whole underbody a more efficient downforce producing device by reducing drag on the car and increasing downforce.
The aft part of a car underbody can be a diffuser. It tries to connect the underbody to the back without producing turbulences so that Bernoulli's principle applies and the pressure increases while the velocity decreases. The side and the roof end in a sharp edge, so that their pressure does not increase. Because the pressure in the back tends to equilibrate, the pressure below the car is lower than on the side and the roof of the car.

[Couch]

Originally Posted by double_n01

i honestly have no clue why there is a mailbox in this bumper? anybody know?

[Appropriate]

It's for fan mail to tell you how much your rear bumper sucks.

[montreal_bimmer]

its ugly...

[chrisE92]

Originally Posted by Appropriate

It's for fan mail to tell you how much your rear bumper sucks.

LOL

[double_n01]

wow you guys are sooo cool, just spend your lives chirping people, NICEEEE, douche bag

[Appropriate]

No problem... anytime.

[Hoothout]

thats the uglyist bumper i have ever seen, the diffuser has no use, it just looks dumb as hell

[MeEmZ]

this car is ugly in its own special way ~_~

[kengi1600]

is this the fast and furious 4 car?

[ALPINE6SPD]

what a shitty kit. The fit is awfull and the whole rear blows. Only a true moron does that to his car.