Ceiling circular aerator, champignon ventilation for caravans

Champingnon vent.
Interior cut hole for tube approximately 8.3 cm.
Total aerator measure of the circular top side by side (oval) is 20 cm.
Height of 3.5 to 7.5 cm that would be the part of the midpoint of the champignon to the ceiling.
For questions of measures call. (very orientative measures).