Cardboard Spool Adapter/Insert

*12/31/24 update: The model has been slightly shrunk to better fit cardboard spools. It should now fit inside cardboard spools comfortably but without needing to jam it in there. A simple insert for cardboard filament spools to help reduce friction. I created this to help print with 85a TPU, which will stretch and warp prints if the filament spool can't spin freely enough. The insert should just reach the other side of the spool.