Axial Duct Booster, Housing Material Galvanized Steel, Fits Duct Dia. CFM at Duct 800/700/600, CFM at 0.000 in. 150°F, Inlet and Outlet Dia. In-Line Axial Fan Duct Boosters Designed for powered air intake and exhaust systems, or to boost air flow in hard-to-heat or -cool areas.