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 12 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 10-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 12 Inch Adjustable Angle Normally Closed Airflow Damper.