A rotary leadthrough of a robot arm, in particular of a fourth axle of a Delta robot, has a housing and a shaft, located in an axial leadthrough of the housing and supported rotatably in this housing, for connection to the robot arm. The housing has at least two openings for cleaning the axial leadthrough. The shaft at least in a portion of its length, has a diameter which is less than the diameter of the axial leadthrough in that region, so that there is a void between the shaft and the axial leadthrough.