Gaiter or gangway bellows for the intersection of two vehicles with a jointed connection

The bellows have a bellows part (10) comprising U-shaped running bellows frames that cover strips made of bellows material under formation of folds or corrugations. A bellows area comprises a closable, flat opening that extends in a longitudinal direction of vehicles (1, 2) over the folds or corrugations, where the opening includes a window element (30) to be detached from the bellows area. Frame strips of the window element correspond to the frames. The strips stay in detachable connection with the frames by a connection unit, and comprise a reinforcement unit coated with plastic.