It might be a little flexible to protect them from my clumsiness. I have a sketching kit of that stiff non-woven fabric with elastic loops to hold those charcoals but don’t trust it. If dropped or squashed even a slight angled impact might be enough to snap them off

Edit: Also the charcoal might rub off on the lining and transfer to my hands, and then get touched onto everything. That stuff is almost as bad as glitter