An open parts tray that stacks: 2mm outer walls, a 1mm divider grid, and a ⌀6 post in each corner topped with a 3mm pin. A matching ⌀3.5 socket is bored under every corner, so the pins of one tray register into the tray above — filled trays tower up neatly and lift apart one layer at a time. Width and depth set the footprint (50–160mm); slots across and slots deep split the interior into equal compartments — leave both at 0 for one open tray. Turn pins off for a plain, non-stacking tray. Print tip: prints flat with no supports. The pins are the only fine detail — if they come out stringy, drop the nozzle temperature a few degrees and they sharpen right up.