So this is a late comment but I finally clicked the link because I am a DMT addict, and lordy that's a cool thing that looks like it will travel just fine.

Which do you find best for traveling? I travel with one of the big DMT fine hones but if I was resorting to something on my keychain maybe I want coarse? When I said I do a "quick repair" I meant I can't correct each knife with only a fine hone, but I can make them better. In that spirit maybe the optimal travel keychain hone size is coarse. Because I don't have all night, nobody else cares, and sharper is better than "prop knife", as another commenter mentioned.

Very cool about the ceramics, I had not thought of that but since we have many crafty ceramics we know their abrasive properties and once you are given the idea huh that's obvious. Thank you!