Covered Dryer Vent locks out the outside air & pests. When outside air enters your home through an exposed dryer vent, that can mean higher heating bills in winter, higher cooling bills in summer. Our Dryer Vent Closure keeps out that outside air. When your dryer is running, the heated dryer air pushes up the floating shuttle, then escapes from the vent's bottom. When the dryer stops, the shuttle drops back down, keeping wind, birds, bugs and rodents outside. Made of ABS plastic, the Dryer Vent mounts easily over an existing 4" vent pipe and can be painted. Screws included. (Not for flexible pipe.)