The Omron E2K-X4ME2 is a capacitive proximity sensor from the E2K-X series, designed to detect both metallic and non-metallic materials through a 12 mm cylindrical plastic body. It runs on 10-30 V DC and switches a 200 mA load, normally closed, so the output breaks when it sees the target. The 4 mm sensing distance is unshielded, which means it can be flush-mounted but with some derating against metal—that 4 mm is the spec value for an unshielded mount. Rated IP66 and NEMA 4/12/13, it handles washdown and oily environments well; the 2 m bare-wire cable keeps installation simple for a control panel or a junction box on a lube route.
If you're looking at the E2K-X8ME1 as a possible alternative, there are two showstoppers that matter in the panel. The E2K-X4ME2 uses a 12 mm diameter body; the E2K-X8ME1 uses 18 mm. That's a different mounting hole—you can't just swap them without re-drilling the bracket or changing the sensor mount. And the output logic flips: the X4ME2 is normally closed (NC), while the X8ME1 is normally open (NO). If your PLC input expects a break signal when material is present, the X8ME1 would give you a make signal instead, so the logic in the program or the input card wiring would need to change. The X4ME2 also has a shorter 4 mm sensing range versus 8 mm on the X8ME1. If range matters for your target, that's another reason the X8ME1 isn't a drop-in. For a true second-source, you'd need both the same diameter and the same output type; no direct ledger sibling matches that for the X4ME2.
The sensor body is 12 mm diameter with a smooth plastic barrel. The 2 m prewired cable has 3 wires. An indicator light is included. No sensitivity adjustment is needed. Operating temperature range is -13 °F to 158 °F.