Abstract: The present disclosure relates to a medical fluid-conducting cassette for a medical fluid treatment that includes a hard body defining channels for guiding fluids through the cassette; a first film section arranged to cover parts of the hard body against an exterior of the cassette; at least one connection point configured to connect at least one of the channels with an exterior of the cassette in a fluid communication; and at least one covering device attached to the hard body and arranged so as to cover the connection point in a releasable or removable manner. In some embodiments, the covering device is a second film section made from the same material as the first film section.