These are heavy duty rod holders. I used the Heavy Duty closet rods from Lowes. An eight foot rod is $27 USD. You can buy them in six foot sections too. The rods are just under 33.75 mm in diameter. One section of rod only requires two brackets. I printed mine with Bambo Labs Basic PETG. I used 7 walls, 4 top and bottom layers, with 15% Gyroid. You could probably go down to 10% and be fine. The brackets are the same width as a 2x4. There is supposed to a 3 mm gap between the bottom of the spool and the top of the bracket to allow the spool to slide past the bracket. An eight foot rod will hold 34 rolls. I print two at the same time. It take just shy of 400 grams and 13:33 to print.