These wristbands have the MiraCool cooling crystals in them - which stay cold for hours but don't leak water out! Stay cool all day, and take some sweet pictures like this one!
I actually do not care to much for these someone needs to look at the website of http://selfcoolingproducts.com they need no refrigeration no water to add and they self regenerate back to keep you cool the next day they say and I have used them for a 30 to 40 min work out and they work great !!!!