For installation in ventilation ducts with a nominal diameter 100 mm (4 inch), for use with tumble dryer vent pipes or hoses, bathroom vents & extractors, air conditioning units, kitchen fans & vents, home wall vents, wide variety of industrial uses Installation : the vent is installed by inserting the nozzle into the ventilation duct. the installation of the rubber seal requires a little bit of patience. the ventilation grille is fixed to the wall using the four included screws. The vent has been re-designed for quietness. the metal flap is sealed from one side to prevent air from entering the ventilation system and to close quietly. a foam stopper has been installed to the inside of the hood to prevent loud rattling when flap opens. so the vent will open and close quietly. The vent is made of brushed stainless steel and is designed for the use of exhaust air systems with higher volume flows. the flap in the housing prevents a rebound of (cold) air.