Abstract: An apparatus (1) comprising a cassette holder (5) which has a bottom wall (6) and into which, at option, a larger first cassette (7) or at least one smaller further cassette (8) can be inserted, and comprising at least one positioning device (37, 38, 39) for the smaller further cassette (8) and a blocking device (54, 55, 56) for the positioning device (37, 38, 39), which locking device serves for blocking the positioning device (37, 38, 39) in its positioning position, the positioning device (37, 38, 39) and the blocking device (54, 55, 56) have been arranged on the cassette holder (5) in the area of the bottom wall (13), and the blocking device (54, 55, 56) and the positioning device (37, 38, 39) are movable into the non-blocking position and into the non-positioning position, respectively, by the larger first cassette (7) when it is inserted into the cassette holder (5).