I designed this after I bought a parkside electric screwdriver and found out that it has a proprietary bit holder. This goes from their "torx" to a regular hexbit size. To keep the bit holder from falling out i showed down a small neodyneum magnet with some superglue in order to hold it in place.

I recommend printing it in a high quality to make sure that it holds up, when printing with 100% infill it seems to be almost as strong as the original parkside bits.

(I am not sure but it would not surprise me if this works for other brands too, I don't think that it's only one manufacturer that uses this bitdesign)