The Dial 78318 20" Multi-Pitch Roof Jack with Damper is a highly-reliable, durable product from Dial. This adjustable roof jack is ideal for the installation of all major brands of residential ducted downdraft coolers. It's made with 28-gauge galvanized sheet metal, and it includes a slide-in "winterizer" damper. It's rails are preinstalled to support an optional Max Aire barometric damper. It's flanged and adjustable for flat roofs and for roofs pitched up to 6/12.