I use this on my MK3S. The intent is to use it with the stock filament roll holder to prevent the filament from flipping off the side of the spool (happens mostly with new spools) and causing problems for the Bondtech gears. It's a simplified version of SquareMesh's with a notch to hold it tighter on the bar.

Re: Large Fusion 360 file : It's large because it has SquareMesh's design embedded in it as a mesh to brep (I traced his design). His has a lot of fillets and rounded corners which makes it much larger.

Print instructions

It's a very simple part. Draft mode and 5% infill works fine but pretty much anything should work.

The included gcode is draft, 5% infill.

Update - June 2025 - No model updates, but my PLA versions of this warped over time and didn't hold onto the frame as well after a year or two. I suggest PETG or something else if possible.