The items in question are called Card Access Wireless Motion Sensors (Model #’s: WMS10-2-C-ZP - Ceiling Mount, WMS10-2-ZP – Wall-Mount, and WMS10-2-EXT-ZP – External Wall Mount). The Wall-Mount version measures 1.8 inches in depth, by 2.5 inches in width, by 3.4 inches in height. The Ceiling-Mount version measures 5.25 inches in diameter. These devices contain an integrated Passive Infrared (PIR) motion detector. They are powered by a 9V alkaline battery, which is included. This device uses PIR technology to detect motion in a room, garage, or backyard. It senses motion and light inside and outside the home by responding to movement or changes in ambient light levels.
[1] Please importantly note that only the relevant portion of the related is displayed above. You may refer to the said customs ruling for the entire ruling explanation.
[1]. https://rulings.cbp.gov/ruling/N272717