The RRD is a round damper that is easily inserted into rigid round ducts for retrofit zoning in forced air heating and cooling systems. This power open power closed damper actuator is available in four sizes for 5 in. 6 in. 7 in. and 8 in. ducts. Features   Easy slide-in installation 2 VA allows for many dampers on one zone Available in 4 sizes to fit most rigid round branch ducts Quiet long life motor automatically shuts itself off in full open and closed positions Gaskets around blade and under motor housing for low internal leakage and very low external leakage Range stops with easy adjustment from top of motor Easy to see and reliable mechanical blade position indicator Easy to hook up with conventional thermostat wire Simple manual blade positioning with push button gear release