These lightweight cooling neckbands are an effective way to combat heat stress no matter what your activity. Durable and washable (and patriotic!), they don't expand like some crystal gel-type coolers. To activate, you soak it in cool water for 1 to 3 minutes and wring out the excess water. Cooling times will vary, but on a typical hot day it can give you up to 8 to 12 hours of relief.