Damper opens with air flow and closes when the air flow stops. Spring loaded with positive closure and a rubber gasket. 4".

Sizes available:
6", 8", 10" & 12"

ThermoFlo 2000 Premium Ducting is specifically engineered to handle unconditioned air. The 2000 SR Series can withstand high heat, high humidity and excessive CFM's without any failure or fatigue.