This is the first OpenSCAD model I ever created, so the file itself may be inefficient but the shelves themselves have held up for 3+ years printed in PLA.

180mm x 150mm stackable shelf. OpenSCAD design file provided to allow for any size shelf to be made.

2 STLs are provided: 2 inch height and 3 inch (I think?) height. Height doesn't include the top, and height is slightly reduced when the feet are nested in the top of another shelf.

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