How do I remove the diffuser pane in my sun tunnel?

If your sun tunnel does not have an internal ceiling ring, you can simply turn the diffuser pane counter clockwise to unscrew it from the diffuser.

If your sun tunnel has an internal ceiling ring, then you have to remove the cover plate by simply clicking it off, moving the small clips to the unlocked position, and the diffuser pane will be able to drop out of the diffuser.