These Proximity Sensors use high-frequency oscillation. They resist heat, chemicals, and water better than Rectangular Sensors. They are available in both shielded and unshielded models.

Proximity Sensors are available in models using high-frequency oscillation to detect ferrous and non-ferrous metal objects and in capacitive models to detect non-metal objects. Models are available with environment resistance, heat resistance, resistance to chemicals, and resistance to water.
Features and Benefit
Read more:https://inaparts.com/sensor/omron-e2ef-proximity-sensor-with-stainless-housing/