The present invention relates to a fluid cassette, for example, a blood treatment cassette (1000) having a cassette body embodied as a hard part (1) and, optionally, a film (3) which is connected to the hard part (1) and at least partially covers the hard part (1), wherein the hard part (1) comprises at least one first alignment device (504), and a second alignment device (505) which are optionally arranged at first and second opposite sides of the fluid cassette or are attached thereon. The invention relates in addition to a blood treatment apparatus (5000).
