TPU Spool Brake insert for Cereal Box Spool Holder (Prusa & SUNLU)

This part is designed as a solution for uncontrolled filament unwinding when using the spool holder by @tcosta. I currently use tcosta's solution on more than 10 dryboxes and I really like it. However, some filament rolls tend to unwind spontaneously due to internal tension in the filament. If filament slips over the edge of the spool, it can jam the entire setup. This TPU insert adds controlled friction to the spool . It is loose enough to allow the extruder to pull filament smoothly, but strong enough to prevent the spool from free-spinning. I put one on each side of the holder to keep things symmetric. Different variants are included because PRUSA and SUNLU spools have different widths: PRUSA 9.5 mm – light braking force 10.0 mm – medium braking force (recommended) 10.5 mm – strong braking force SUNLU 11.0 mm – light braking force 11.5 mm – medium braking force (recommended) 12.0 mm – strong braking force Printing Material: TPU (95A recommended) I used SUNLU 95A TPU Nozzle: 0.6 mm (0.4 mm should also work, but not tested) No supports 2 perimeters 3 top & bottom layers 20% infill (infill percentage is not critical due to low internal volume)