We all have that room that doesn't get used all that often. Don't waste precious resources (and money) heating and cooling your guest room or living room when the Suncourt ZoneMaster 8 Inch Adjustable Angle Normally Closed Airflow Damper lets you tend to the temperature on an as-needed basis.This normally closed airflow damper is made from durable metal with an easy-to-install 2 wire installation design with a free-wheeling coupling for a snug, permanent fit. Its 8-inch diameter design is normally-closed, design to close off your HVAC ducts, funneling air where it's needed the most. When you need whole-home service, just switch the damper from closed to open (or between) with your controller.The adjustable powered HVAC damper is designed to work with existing zone-controller systems and can also be used as a standalone device with the included 24-volt transformer unit. Take control of your home's energy with the Suncourt ZoneMaster 8 Inch Adjustable Angle Normally Closed Airflow Damper.