After having replaced my side-brush module, and then having the brushes break, then replacing the brushes with a TPU brush and having it strip out on the hex mount... I decided to reengineer a bit of it. This version allows for the TPU brush with a larger splined shaft to prevent strip out. It also includes a new replacement gear with the splined shaft. Last, it includes the cover with enlarged opening to accommodate the larger shaft. The replacement cover was necessary because mine shattered and the gear rides in a little shelf area with in the gearbox. The collar is used to offset the driving gear from the up conversion gear, so they don't rub. Make sure to use some grease to prevent friction and prevent parts from failing.

The brush with a spline fitting can be found here: https://www.thingiverse.com/thing:7011892

Brush - TPU print (95A) - Allowing thin walls will help print with the brush ends (1 wall thick strands) Gear - (Nylon preferred) ABS/PETG (I used PLA and so far it has worked fine for a few months - then I reprinted it in PLA+ [I don't have access to nylon printing atm]) Cover - PLA/ABS/PETG

Attribution: Thanks to Devise3D for the base gear model which you can find for free here: https://www.cgtrader.com/products/roomba-series-675-corner-sweeper-drive-gear Thanks to OhSnap for the base brush model design: https://www.thingiverse.com/thing:2645821

Note: I did make the teeth on the gear have more length to accommodate FDM effects. Blender files included. Admittedly, the top of the cover doesn't look amazing, but I wanted the clean precision on the inside of the cover, so I printed it upside down.