Some people seal the Rear Seat Air Vent, some don't... As of now I plan to use it. I purchased the Rear Seat Vent from SFSA but their air box is too small and didn't fit inside as described in the instructions. I decided to fabricate the air box to allow a better fit. I made a template out of some heavy stock paper and then cut the parts from some scrap aluminum. When it's finished it should look very nice. A fairly simple project which was kind of fun.