This is the first OpenSCAD model I ever created now updated in 2025 with a cleaned up OpenSCAD file that no longer require external libraries!

180mm x 150mm stackable shelf with a height of roughly 2.5 inches (you lose some height between the nesting of the legs). The OpenSCAD design file is provided to allow for any size shelf to be made, with an option to include the holes on the top or not.

Supports NOT needed. When printed upside down, the hole has a roughly 45 degree interior angle so it shouldn't have any issues with overhangs.