DiGiYes M12 Proximity Sensor Switch LJ12A3-4-Z/BX Detecting Distance NPN NO DC 6-36V 4mm Inductive Proximity Switch

Got this one to add auto bed leveling to a 3D printer. Works perfectly for that usage. Make sure you get the right type! PNP/NPN, NO/NC. Also check the voltage. For my application, voltage range is great (my 3D printer is 24V, some are 12V), and NPN was what I needed. As expected the measuring distance is very repetitive which is what I needed. I like the LED on the base of the unit, helps make sure everything works as expected.

These sensors come in both NPN and PNP. Also they are either normally open or normally closed. Make sure you know which you need before ordering. This sensor works great. I replaced a mechanical limit switch on a CNC that occasionally would get bits of wood in it. This works and it's extremely precise. I did a test where I measured the distance (using the CNC so accurate down to .001") several times. Each time the measurement was less than the machine could measure.