It is an M18 barrel-style sensor, a common form factor for industrial position sensing in automation lines.
As an inductive proximity switch, the SIEH-M18B-PS-K-L-CR detects the presence of metal targets without physical contact. M18 barrel sensors are typically mounted via a bracket or through-hole in a machine frame, with a cable or connector running back to a PLC or I/O block. The SIEH series is FESTO's standard line for this class of sensor.
