This is just a quick spool adapter I made to use with Hatchbox filament spools with a 1.25 inch hole (32mm). It's designed for use with horizontal spool holders with a center rod. You'll need one for each side of the spool. Files are labeled for the diameter of the two spool holder rods I use. The "hatchbox_11mm_rod" has a 12mm diameter hole The "hatchbox_8mm_rod" has an 8.5mm diameter hole It is a tight fit, so it will take a little pressure to get in. It's easiest to insert the first two "arms", then fit the next two one at a time.