iPower 4 inch Backdraft Shutter Damper Back Draft Blocker, One-Way Airflow Ducting Insert Backflow Preventer with 2 Inline Springs Loaded Folding Blades, 4", HVAC Extractor Fan Vent, Range Hoods

iPower 4 inch Shutter Back Draft Blocker, One-Way Airflow Ducting Insert Backflow Preventer with 2 Inline Springs Loaded Folding Blades, 4" Backdraft Damper, for HVAC Extractor Fan Vent, Range Hoods

EesTeck 4" (Diameter) Adjustable 304 Stainless Steel Duct Clamps Hose Clamp Pipe Clamp Air Ducting Clamp worm drive hose clamps (4Pcs, 91mm-114mm)

AC Infinity Flexible 4-Inch Aluminum Ducting, Heavy-Duty Four-Layer Protection, 25-Feet Long for Heating Cooling Ventilation and Exhaust