A single blade round damper with a (2) two position, 24 volt motor. The motor is powered both ways - powered open and powered closed. The motor features LED's that indicate the position of the motor whether open or closed. The LED's are colored RED for closed and GREEN for open. These indictors are a failsafe measure meaning that they will not illuminate until the blade of the damper has gone to its full open or full closed position. The motor is a 3 wire hook-up with a common, a power open leg and a power closed leg. The available sizes are 4" - 6" - 7" - 8" - 9" - 10" - 12" - 14" - 16"-18"-20". It can also be purchased with an S1A end switch, as a URD-L (no motor), or as a URD-LM24 SR-T (modulating motor).