Plug-in, permanently lubricated motor-engineered for continuous operation. Dynamically balanced centrifugal blower wheel for quiet, efficient performance. Low RPM for quiet operation. Rugged, galvanized steel construction. Metal, 4 inch oval duct connector with no metallic clatter. Includes 4 inch oval to 3 inch round duct reducer. 4 inch height allows for 2 x 4 wall or ceiling installation. Sturdy, easy, mounting directly to stud or joist. Can be mounted in flat ceilings, sloped ceilings up to 12/12 pitch and walls. Polymeric construction. Innovative design-the result of extensive research with designers and consumers. UL listed for use over bathtubs and showers when connected to a GFCI protected branch circuit.