They're vents for the body of the car, when you slam the door or run the HVAC blower on higher settings the air pressure created vents out of those valves in the body work. On sedans and crossovers they're usually hidden under the bumper covers.What are those two rectangular black and gray things mounted to the back?
And they make a lot of noise on the outside from the subwoofer I have. I’m looking to add sound deadening to the rubber flaps on them to make them a little heavier.They're vents for the body of the car, when you slam the door or run the HVAC blower on higher settings the air pressure created vents out of those valves in the body work. On sedans and crossovers they're usually hidden under the bumper covers.