The adapter frame ( article 1204) is mounted between the MIDI-HEKI installation frame and the roof panel.
The frame creates a horizontal and straight installation situation for roof hood mounting.
By default, the mounting surface on the X250 is too small for a "clean" roof hood mounting.

There are van manufacturers who install an adapter frame as standard for the benefit of long-term tightness (e.g. Pössl and Globecar).
However, many manufacturers do not install an adapter frame.