I love two-ring binders. It's convenient to change pages and sort them, and the paper is less damaged with only two holes. The spine of a two-ring binder is usually thick, and it can only open flat. So I made a two-ring binder with a thin spine, so that it can flip all the way around like a notepad.

It has the neatness of a traditional two-ring binder and the folding function of binder rings, but it will not be as loose and messy as binder rings.

The rings are about 24mm in diameter, separated by 80mm.

How I printed mine
- 0.2mm nozzle, 0.1mm layer height
- Bambu PLA Basic
- 2mm outer brim for rings; no brim needed for spine
- Normal support enabled for printing the ring openings

Check out the 12mm diameter version for loose-leaf papers.