The cat door did not come with anything to cover the space between the front and back pieces, leaving an ugly view of my hollow door. It is sized for a 22mm gap, the parametric model is included so you can resize or remix. 

The flat brim that fits on the back piece is spaced to allow double sided tape. If I did it again, I would put the brim on the front piece (smaller opening) and glue the print to the back piece. That would allow you to screw the front firmly to your door and press the two pieces together. I had to use a few drops of super glue on the front piece making mine a more permanent installation.