In development for 2 years with Cool Tekwear, 661 and Bob Hannah..... Used by fire fighters, first responders, military personnel, athletes and race teams, the SIXSIXONE Core-Cooler Personal Radiator™, works by utilizing the latest advances in Polycrylamide Cross-Linked Polymer technology. PCLPs are non-toxic, hypoallergenic and completely inert plastics, which absorb liquids. The 661 Core-Cooler's specific compound of PCLPs uptake water at a rate of 500:1. Soak the Personal Radiator in water for as little as 5 minutes, or up to 120 min. Allow to dry, Velcro the "661 Core-Cooler" on and stay cool for up to 5 days.