This is a FESTO Type SMT-8-NS-K-LED-24 sensor.
Flat design for insertion in FESTO Air Cylinder groove.
A 3-wire solid state switch with LED indicator light.
Sensor  is used - has been tested - with 90 day Warranty.
Actual picture if item.
Price $15.00 ea. (6 available with 20 inch cord)
Price $13.00 ea. (12 available with 8 inch cord)