With the Hario Slim Coffee Mill I think we have found the best travel grinder out there. I have used them all, and if you are brewing small amounts of coffee out on the road, this is the best.
Why? The grind quality from the ceramic burr set is very good. The narrow shape allows a good grip on the mill while grinding coffee. The hopper has a lid so coffee doesn't spill out while using it, and it is made of durable plastic, so there is nothing to break. It weighs 245 grams (1/2 Lb) so it is light as well.
The larger Hario Skerton mill has more capacity (about 3 times as much), but if you are brewing for 1 or 2 people, I think the Slim model is ideal. And it costs about the same so pick the one seems to be closest to the amount you usually grind. I would say it is a perfect one or two cup mill; if you make more than that, use the Skerton. I traveled through Sulawesi and Java for 2 weeks, and the Hario Slim proved functional and durable, the grind quality was awesome, and the coffee we had for ourselves was a lot better than the local crappy Robusta they serve!
Approximately 6 inches high and 3 inches wide. Pretty self explanatory, which is good since all the instructions are in Japanese. There are one and two cup markers on the barrel where the gound coffee lands.
The Hario Slim Mill has a conical burr design, so it can do a range of grinds from espresso to a passable French press grind (on the finer side of French press). The grind adjustment is on the underside of the burrs. Use the handle to hold the spindle in place and twist the wing nut to open or close the burrs. There ought to be a slight clicking sounds as you make the adjustment. There is no marking on the adjustment - it is stepless - so it may be problematic in terms of going back and forth between different settings. The grind setting does not lock into place like on the Skerton mill so the setting can drift during use, not badly though.
Take a look at this Tiny Joy newsletter we dedicated to comparing the Slim against an electric blade grinder and a much more expensive electric burr grinder.