These are great, but tend to cool down too fast. When skiing or snowboarding it is very cold outside, and taking off the glove to "refresh" (shake and expose to air) the warmer isn't easy. Moreover, this "refreshing" doesn't keep it warm for long enough. I think that these warmers are a must-have when skiing or boarding, and should be in everyone's gloves, but note that although your hands won't be cold, they also won't be warm. Cheers.