Filament guide wheel

thingiverse

This is a filament guide wheel with a deeper groove that supports a mini ball bearing (12.7mm - R3ZZ) in its center. Other guide wheels that I've tried were quite shallow and filament could easily escape. I used the bracket from CSMachineCo (https://www.thingiverse.com/thing:4735175) with a minor modification (drilled a hole and used an M5 screw). You can use other brackets with wider arms and you can modify only the Z dimension to make the wheel thicker (possibly supporting two ball bearings).