Siemens 3RG7135-3BE00 is a SIMATIC PXO230 L18 laser thru-beam sensor — the transmitter half of a pair, straight optics, in an M18×64 barrel. It runs on 10-30 VDC, reaches 50 m, terminates in an M12 4-pole connector, and seals to IP67. That 50 m range with a laser beam means you can punch through dust or fog across a long conveyor or crane bay where a standard LED thru-beam would scatter.
The M18 barrel and M12 connector are common footprints across the SIMATIC PXO family, but the laser optics and 50 m range are specific to this variant. If you're swapping an existing 3RG7135-3BE00 on a live line, verify the receiver model — the thru-beam pair must match wavelength and modulation. The IP67 rating handles washdown and outdoor enclosures, but remember the lens needs periodic cleaning in dusty environments to maintain the full 50 m.