Round light barriers, GR18 Inox, GRTB18S-N2431V, switching distance max.: 3 mm ... 100 mm, sensor principle: reflection light sensor, detection principle: background suppression, switching output: NPN, switching type: light/dark switching, connection type: M12 connector, 4-pin, light transmitter: PinPoint LED, setting: none, communication interface: -, included in delivery: fastening nut (2 x)