8.5" x 6" vent duct cover - cold air return register with back side trim ring.

This vent will fit in an opening 220mm x 156mm ( approx. 8.5" x 6" ).  We designed this based on a specific need, so it is an unconventional size.  A 19mm flange surrounds the vent opening. it is 20mm deep.  Since This vent was designed for a door, we added a back trim flange that will cover the back of the opening .  The flange will slide over the back side of the vent.