Insert for Cardboard Filament Spools

Cardboard spools are used more and more often for 3d printing filaments by various brands. Those spools show increased friction when put on simple spool holders that carry the spool through its central opening, like on UltiMaker printers.
This inserts reduces friction significantly if printed in a wear resistant and slippery material like a tribo-material and/or by a method that produces smooth surfaces like resin based 3d printing methods.