Panasonic FV-VS43R WhisperValue/WhisperValue-Lite 4" Oval to 3" Round Duct Adap Fire code rated Connects a 4" oval duct to a 3" round duct Works with all Panasonic WhisperValue and WhisperValue-Lite models, including: FV-05VS3 FV-08VS3 FV-10VS3 FV-08VSL3 FV-10VSL3