This is the device that alerts a homeowner when mail has been delivered. The system is comprised of a motion-sensing transmitter that secures to a mailbox door or lid via included adhesive tape and a cordless receiver that beeps and illuminates a red LED when a postman opens the hatch. Easy to install, it requires no wiring or mounting hardware and the receiver works within a 300' range. Includes A23 battery for the transmitter and AC adapter for the receiver. Transmitter 4 1/4" L x 1 1/2" W x 1" H, receiver 4 1/4" L x 3 1/4" W x 1" H.