This tool has the most generic sizes that a housing sparky would use.

I have made it with the total diameters so the apprentice can't get it wrong (hopefully)

This design is different due to being thicker then others I have used before. Also having a larger hole for your standard 3.5mm Flatblade in the centre as well as larger holes to fit a broader range of markers, pens, pencils.
The design has been made thick enough to be left on the dash and not fall apart compared to others that I have used.
For a more presentable look I would increase the top layer shell from 3 to 5.

Also enabling a prime tower for the perfect contrast in colours.

Personally I dont mind due to it reducing the costs and printing time.

If required I can design a similar model that is smaller up to 300mm