The one in the picture is designed to restrict airflow to make the passengers colder. Although some mistakenly believe it is supposed to produce a "ram" effect, forcing more air through the fan. But since the fan CFM throughput decreases with the increased static pressure caused by sucking through a smaller straw, any benefit is most likely negated.
Oh, and hey, they look cool.
Originally Posted by icnsltmfg
What is the consensus of having the heater inlet vent covered or not...does it restrict airflow in thru the cabin? What is the real purpose of the covers?