PMMA tubus for sealing and protecting a safety light curtain of 75 cm length of the series "PSEN op/1". The IP protection class is increased from IP65 to IP67, IP68 and IP69K. The Gore-Tex membrane on the caps prevents the ingress of dirt and water, and internal condensation. The connection cable of the light curtain is fed through a M16 PG cable screw connection and it stops the ingress of dirt and water.