If you have brushes, you want to protect their bristles. Some brushes come with dedicated clear cylinders, which go over its bristles. However, some brushes don't come with them, and they're also quite easy to lose. Furthermore, the cylindrical design of those brush protectors can make them hard to put on the brush without damaging its bristles. Lastly, if your brush is of an unusual shape (like the one in the pictures), you might not be able to find a brush protector that fits.
This is a generic brush protector, suitable for any size and shape of brush (with some scaling). It's designed to be put on handle-first (not bristles-first) to avoid damaging the bristles, and can be scaled for any desired length, or shape, of brush. It is also meant to be printed in spiral vase mode, which uses very little material.
These settings assume PrusaSlicer (or SuperSlicer):
You can scale this in X and Y (if you have a thicker brush) or Z (if you have a longer one). You can also scale X independently of Y if your brush's handle isn't cylindrical: this is easy to do in the slicer.
For material, I used KiwiFil rPETG, but another PETG would work just as well. PLA is not a suitable material for this print, as it's too brittle. Flexible filaments would work well too, but I haven't tried them.
The pictures show the way you can remove, and put on, the brush protector. You want to insert into the ‘wide end’, handle-first, and remove by pushing towards the ‘wide end’ from the base of the handle.
The author marked this model as their own original creation.