Just before Christmas we started stocking a German brand called PICA. They specialise in marking tools which are cleverly thought out. One example is their alcohol-based markers- you might have a Sharpie marker on hand, but if you need to mark or trace out something, that wide nib is not going to do it. Enter the PICA Deep Hole marker. (We also have it in red and blue). Adam Savage does a better job of explaining-
The quiver/holster allows you to protect the nib and also keep dirt and debris away from it and also stops you from losing it in your workshop.
It's also telling that most of the PICA mechanical pencils have a similar form of narrow nibs- check them out.