Superior AK4 4" Outside Air Kit with Collar, Hood and 3' Flex PipeInstallation of outside air kit should be performed during rough framing of 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 Complete outside air kit Optional venting accessory for Superior fireplace Specifications Model Number AK4 Catalog Number F1091 Diameter Size 4"