The file 'Spool Sleeve (Overture) 3D Printer Model' is (stl) file type, size is 31.1KB.
I have an upgraded spindle holder (https://www.thingiverse.com/thing:4368727) on my Ender 3 v2, and recently bought a roll of filament from Overture with a cardboard spindle, but no solid tube in the middle, just two ridges of cardboard that my holder didn't like (kept falling off the bearings).
I printed this very basic sleeve, no supports needed, thin, re-usable, fits snug and does the job.
Cardboard_Spindle_Sleeve.stl | 155.0KB |