Yeah, they work pretty well, but you have to keep feeding them, and only small pieces that will fit in it as you do. I used some of the shredded wood to act as my tinder, and a hand full of small twigs that came from a dead limb that recently fell out of the neighbor's maple tree.
It took about three feedings of the broken twigs and a couple of hand fulls of the shredded wood to get the soup I mwade to a boil, but it only left a tiny bit of ash and un-burnt twigs behind. Very little evidence that I had even been ther at all, and if you are trying to keep a low profile, this isn't too bad as far as that goes. A can of Sterno would have left none, but still...not too bad at all.
