This is a very simple replacement fader cap for most professional audio mixer consoles or (DMX) light consoles. It will fit the standard 2mm × 1.2mm fader levers.

In the images above the grey fader caps are original Behringer caps, the brightly colored ones are prints of this model.

You can print it in any material with standard infill. Don't try to use 100% infill, since the opening for the fader needs to be slightly flexible. Print it with the fader mounting hole down. On Prusa printers you can ignore the “low bed adhesion” warning, no brim is necessary. The example GCode files use PLA with standard 15% infill on a smooth print sheet - I had good success with these settings.

You can use them as-is or you can add a piece of filament to add more color. In my experience: use some filament color with high contrast to the cap itself - that makes it easier to use in a dark theater.

The middle groove is exactly big enough to fit the standard 1.75mm filament - simply add a very tiny drop of super glue into the middle of the groove, gently press a piece of colored filament into the groove - the piece should be a bit too long for the cap. Wait a few seconds for it to dry and then cut off the ends to make the filament flush with the cap - use a sharp cutter knife or wire cutters.

I included the FreeCAD design if you want to change it or use it as an inspiration - the sketches are named to be easily recognizable. It was originally designed with FCad 0.21, but also opens fine with version 1.0. Feel free to use the design any way you like.