There are many, many overdone field knife sharpeners on the market but very few that I would consider carrying regularly. That is why I love my USA-made, easy-to-carry Hewlett Two-Sided Diamond Sharpeners with medium (600) and fine (1800) grits. I have had a couple of these knocking around for years now. It might be the most versatile, easiest-to-carry, field sharpener I own.
These diamond plates are the right size – small enough to carry in their included sleeve and large enough to actually work. They are just under 4″ long, 1.25″ wide, and just about 1/16″ thick. They weigh just over 1 ounce.
I rarely use the medium side but it is coarse enough to get some mild reprofiling done in the field should you take some chips out of an edge. The fine side is all I usually need to touch up an edge before finishing with a quick strop.
I have even used mine to strike a ferro rod and scrape tinder like fat wood thanks to the crisp edges on the plate. It isn’t meant for that and I am sure it isn’t good for it… but it works.
I bought mine on Amazon: Hewlett Diamond Sharpener Medium/Fine