This ceiling mount PIR (passive infrared) motion sensor is 1 of the smallest 360° ceiling mount detectors available today. It is designed to be mounted in small to medium size rooms floor coverage of up to 22 ft. and ceiling height up to 7 ft. High. It blends inconspicuously into any decor. Optimal performance is achieved when the detector is mounted on the ceiling in the center of the protected area. 2 per pack.