Parametric bushing

I created parametric bushings in OpenSCAD to couple my filament spools with my spool holder. Since the model is fully parametric you can change the size of the bushing and the required sturdiness pretty easy to adopt for different usage scenarios / axis diameters.
The center hole is smooth enough to slide on wooden dowels pretty great. When I give my spool a gentle push it moves on for 2 to 3 more turns.
I have included the created STLs for spools from orbitech and bitsFromBytes.