The present invention describes a blown film extrusion line (1), which has the following features: an annular die gap, from which the film tube (9) can be extruded, a flatness unit (7,13) or nip rolls (8), which fold the film tube (9), a calibration basket (20,30), which is disposed between the die gap and the flatness unit (7,13) or nip rolls (8) and which comprises at least two film-guide elements (31), using which the film tube (9) can be guided in such a way that it retains its round cross-section, the diameter of the film tube (9,43) being adjustable by changing the relative position of the at least two film-guide elements (31). The coupling means (32,33,35,38,39), which couple the movement of at least two film-guide elements (31) to each other, are particularly advantageous.