Abstract: A seating surface part and a backrest part are connected to each other in such a way that they can pivot around an axis and thus be folded together into a collapsed position. Retaining belts are provided for the seating surface part and to the backrest part, which has a spacer device on the outside surface facing away from the seating surface side. This spacer device projects out beyond the outside surface of the backrest part when the seat is in use. A retaining device which can be connected to an adult seating unit is provided on the backrest part.