In-line model has removable access panel and no insulation Quiet automatic backdraft dampers Two polymeric centrifugal blower wheels Can be ducted horizontally or vertically Use Broan Electronic Variable Speed Control to adjust blower speed and sound level (available separately)Amperage: 1.4 CFM: 406 Collection: LoSone Duct Size: 4-1 2 x 18-1 2 Finish: Galvanized Steel Function: Utility Fan Heater Included: No Housing Depth: 11-3 4 Housing Length: 21-1 2 Housing Width: 12-1 4 Humidity Sensing: No Installation Type: In-Line Light Included: No Motion Sensing: No Sones: 1.6 UL Listed: Yes Voltage: 120 Wattage: 146 Weight: 33.90