The First Alert PIR725 Motion Sensor is a popular choice among customers looking for a reliable and affordable motion detector. It is designed to work with the First Alert security system, providing accurate motion detection and alerts. The motion sensor has a wide detection range and adjustable sensitivity levels. It can be easily installed in any desired location and is battery-powered for convenience. The First Alert PIR725 Motion Sensor is praised by customers for its reliability, affordability, and user-friendly interface.