Ventilation grille (square)

modified thickness of outside part from 5mm to 3mm, adjusted square size to fit my needs 139x139mm

Inside square dimensions 139x139mm (will fit chimney cutout square of 140-143mm, it goes deep enough to secure itself, my hole was unregular size going any ware from 139-143mm and it sits nicely)

Outside dimensions: 177.8x177.8mm (this will nicely cover any imperfections of the chimney cutout)

Cover overlaps 19.3mm (this will hid any imperfections on the wall)

Added ear brims to prevent warping, more added on printer vent side, if you use my print profile it should come out with no problems, I suggest also to leave gyroid infill as it is.

I have used PETG for the print.