Kit Part No. DAMPACT45DEG-R and DAMPACT90DEG-R are the replacement actuators designed for residential dampers. These kits contain the actuator, an anti-rotation mounting screw, and an Installation Instruction. They can be used on dampers having round shafts or the newer dual flatted shafts. The 24-vac direct-drive actuator provides smooth, quiet performance in a smaller package. The DAMPACT45DEG-R kit is intended for round and newer rectangular dampers having a 45 degree rotation from closed to open. The DAMPACT90DEG-R kit is for slip-in and older rectangular dampers which rotate through 90 degrees from closed to open. Ninety degree rectangular dampers have round shafts while 45 degree rectangular dampers have dual flatted shafts with an arrow on the shaft end.