CatMate Elite 355 Cat flap extension tunnel

The tunnel extension pieces cost a fortune if you can find them. The extension's joggle loosely fits on the original white cowling, and butt up additional pieces to achieve the desired depth (of wall). I've included only a 50mm extn piece, but if you're over you can reduce a few layers using a craft knife.

I've included an end piece that pushes everything neatly together. As you can see, the whole in the wall (for me) is too big to use the existing mounting holes, hence the bizarre mounting brackets.

Printed solid in black PETG (to hide the pigeon blood).