I've cooled off a little on these tiny reusable hand warmers, but I still think they're a mighty good thing to have in the right conditions.
I took one out this morning during my long run and activated it right at the beginning -- it was a balmy 30-somthing degrees. It caught a fair amount of cold air as my friends passed it around, and then I tucked it in my glove and ran away.
20 minutes later it was cold. Not too far off, though, from the advertised 30 minutes of heat.
This is still a great little product for short outings, and it heats up so fast that it's a great way to zap frozen hands in a flash. But if you're going out to play for longer than a an hour or so, you're going to have to stick with the disposable warmers, which tend to last all day.
Update to the update: I forgot to mention that these little guys don't get so hot that you can't put them against your skin. Even inside my glove it didn't make my hands sweat. I have had to wear glove liners with some other reusable warmers (or put them in a pocket), because they get so hot they burn my skin.
Sara Davidson is an ultrarunner and our resident women's gear destroyer.
