Durable Material:The body is made from galvanized iron and the flap blade is made from aluminum, durable material for long-lasting performance. Constructed with sturdy components to ensure reliability.Size: Port Outer Diameter: 199mm / 8 inch; Length:88mm / 3.5 inchAutomatically Open and Close: Enjoy a comfortable environment with our Backdraft Damper, designed to automatically open and close to keep unwanted air out. Say good-bye to drafts and temperature fluctuations as this damper effectively blocks cold or warm air from entering your space.EPDM Rubber Seal Ring Inside: Experience noiseless and quiet with our Backdraft Damper featuring an EPDM rubber seal ring. This innovative design ensures smooth and silent operation when the flap board opens or closes.