I can tell you that they do work! At least out in arid Wyoming summers.
I also have the cap thingy that goes under a helmet or under a ballcap. Used it last summer while baling hay under my ballcap. It's great! Also have the neck cooler. I suffer terribly from the heat and this makes it more tolerable.
I also bought a vest for my son who rides dirt bikes out here and doesn't tolerate the heat well either.
Personal experience is very positive and I highly recommend. Don't know how/if they work in more humid climates.
When governments fear people, there is liberty. When the people fear the government, there is tyranny. Thomas Jefferson
