Superior 4-inch Outside Air Kit with Collar, Hood and 3' Flex Pipe AK44 inch Superior Outside Air Kit with Collar, Hood and 3' Flex Pipe AK4 Product Details Installation of an outside air kit should be performed during the rough framing of the fireplace due to the nature of its location. Outside combustion air is accessed through a vented crawl space (AK4F) or through a sidewall (AK4). What's Included Outside Air Kit Collar Hood 3' Flex Pipe Features Business & Home Security Complete outside air kit Optional venting