The standard spool arm on the Lulzbot Mini has a square top, which doesn't mesh well with the round interior of a filament spool. Especially with full/heavy spools, the square corners supporting the round spool hub can cause uneven tension and jerking.

This spool bushing is 50mm in diameter, which works well with most standard spools that have 52-57mm ID hubs. Simply insert the bushing into the spool, and then slip it onto the Lulzbot Mini's spool arm. It provides a long, curved surface and therefore even tension, with no modifications to the standard spool arm. Easily removed for small diameter spools (like the Taulman spools, for example).

Sketchup design file included.