The Lulzbot Mini comes with a spool holder that's rectangular in cross section. Filament spools are round and they pivot and hang up on the arm as they are de-spooling. This circular bushing attempts to smooth out the situation.
Original
lulzbot-mini-spool-holder-bushing.scadlulzbot-mini-spool-holder-bushing.stl
With added flange
lulzbot-mini-spool-holder-bushing_w_flange.scadlulzbot-mini-spool-holder-bushing_w_flange.stl
Uploaded to thingiverse as http://www.thingiverse.com/thing:1413572
"Remixed" from http://www.thingiverse.com/thing:1353400