The invention relates to a calender for treatment of a product web, having at least one roll stack comprising rolls arranged in a calender frame, the ends of which rolls are guided in roll mountings, which can be fastened to the calender frame by means of brackets, and having guiding means associated with the rolls for guiding a product web through nips formed between the individual rolls. For a rapid change-over with respect to the nature and intensity of the treatment of a product web in a calender, the brackets are in the form of modules, which support the rolls and are capable of being fastened individually to the calender frame and which have identical connecting devices for grouping, as desired, on the calender frame.