I made this to fit on this microphone arm.  The smaller center keeps the roll more balanced and easier to spin.

These are spool inserts for cardboard Overture rolls (~55mm diameter).  Two variants:  just the rim and a ribbed design with a 21mm diameter.   No supports needed.

Design files are for SolveSpace and include a outer-rim, the ribbed center, and the assembly of both.  STLs from SolveSpace were imported to PrusaSliver and re-exported to clean them up (SolveSpace often produces STLs with “repairable errors” that are just fine).   To edit the dimensions should be fairly easy; so have fun – I thought these might make a nice reference for someone that is not just Fusion360 or FreeCAD files from a much simpler system.