What this 4 mm sensor is and where it fits
The E2EC04S12MCB1OMS is a flush-mount inductive proximity sensor from Omron's E2E series, built in a stainless steel barrel just 4 mm wide and 4 mm tall. Its compact form factor fits where larger M8 or M12 sensors won't — think tight gripper fingers, small linear slides, or embedded into a fixture. The 1.2 mm sensing distance means it detects small metal targets at close range; paired with a 4 kHz switching frequency, it picks up fast reciprocating or rotating parts without missing a count. Rated IP67 and housed in stainless steel, it holds up in coolant splash, washdown zones, and metalworking environments where brass or plastic housings might corrode or crack.
How it compares to the closest second-source candidate
The often-paired alternative is the E2BS08KS02MCB120OMS, a flush-mount PNP NO sensor from the E2B series. On paper it offers a longer 2 mm sensing distance and higher 200 mA load current, but the body is an M8 barrel — 13 mm diameter — so it physically will not drop into a panel cutout or bracket sized for the 4 mm E2E. If your application has the mechanical room, the E2B carries IP67 and stainless steel too, but rewiring is minimal since both use the same M8 3-pin connector. For a true drop-in replacement without redesigning the sensor mount, stick with the original 4 mm form factor.