The FESTO SIES-V3B-NS-S-L is a proximity detection switch with a 2 mm operation distance, classified under Limit and Proximity Switches.
The 2 mm operation distance means the sensor triggers when a ferrous target approaches within 2 mm of its sensing face — typical for detecting piston position in a Festo cylinder or confirming a part is present in a fixture. This is a short-range, precise detection zone suited for tight-clearance applications where a longer-range sensor might pick up background objects.