The part number 9816729980 is a OEM ride height / headlight leveling sensor for PSA Group vehicles (Peugeot and Citroën).

Specifically, it fits:

Peugeot 508 / 508 SW

Peugeot 5008

It is typically mounted on the front suspension (left or right side depending on the specific application) to monitor vehicle ride height and automatically adjust the headlight beam level.