Comparing the connector variants
The E3Z-R61K-M3J: The standard variant E3Z-R61K uses a 2 m pre-wired cable. The M3J suffix here swaps that for a 0.3 m M8 quick-disconnect pigtail. Same sensing head, same 3 m retro-reflective range. If your panel uses a fixed wire run, the E3Z-R61K is a direct fit. But if you need a modular field-replaceable connection or a short pigtail to a junction box, this M3J version saves the crimping. Does it cross to what you've got? Only if your wiring scheme expects an M8 connector, not a free cable.