The present invention relates to a medical fluid-conducting cassette (1000) for a medical fluid treatment, comprising: a hard body (1) comprising channels (49) for guiding fluids through the cassette (1000)； a first film section (3) arranged to cover parts of the hard body (1) and arranged to cover at least one of the channels (49) against an exterior of the blood cassette (1000)； at least one connection point (41) configured to connect at least one of the channels (49) with an exterior of the blood cassette (1000) in a fluid communication； at least one covering device attached to the hard body (1) and arranged so as to cover the connection point (41), releasable or removable, wherein the covering device is or comprises a second film section (3') made from the same material as the first film section (3).
