Roller blind box and roller blind system

The cassette (100) has an opened hollow section (110) that is extended in longitudinal direction and comprised with a slot (112) whose edge portions (112a,112b) are arranged opposing each other. The opposing ends (110a,110b) of the hollow section are connected by a connecting bar (120). The connecting bar is connected with the edge portions using a connecting unit, by positive rotation of the connecting bar relative to the edge portions.