The 72mm ID Sunlu on filament rolls not unspool as smoothly from a rod style spool holder as the 50mm ID industry standard plastic spools do. The larger hole allowing for a greater lever arm mixed with stiction lead to in a stick/slip motion while unwinding. This uneven unwind can translate into visible print artifacts. This printed hub can help the spool unwind more evenly.

I have tried to minimize material usage and print time. On my printer the two halves press together after printing with a satisfying fit, but they can be wiggled back apart later when the spool is empty for reuse on the next one. I print with 0.5mm extrusion width, one perimeter 0% infill (to avoid unwanted gap filling during printing).

I have included the native solidworks 2018 file, the step file, and an STL. So if the dimensions need some tweaking for your application please feel free to modify as you see fit.