The E3S-AD81 is a diffuse-mode photoelectric sensor from Omron, with a detection range of 20 cm. No separate reflector needed—it picks up the target's own reflected light. Common for presence detection on conveyors, bin-level checks, or part-passing in tight spots where you don't want to mount a through-beam pair.
Marked as current production, so no last-time-buy clock is ticking. This is the part to quote against a BOM line without worrying about obsolescence pushing a redesign.