BROAN NuTone S99020271 Fan Blade 321702 401 you ensure HVAC system reliability you ensure HVAC system reliability and restore the unit's modulation logic to original equipment manufacturer specifications Streamlined Installation: Features a standard 3 4" Chatleff connector for a bolt on fit without the need for custom brazing adapters Ensure you verify the rotation direction (CCW as viewed from the discharge side) and shaft diameter to maintain static pressure performance and prevent premature motor failure in the field it is a frequent replacement part for specific power attic vent models that utilize the 10 inch plastic sweep configuration