The Chill-Its 6715 Hard Hat Cooling Top Insert straps into hard hats to deliver 4 hours of cooling relief. Low-profile and lightweight liner pad features cooling acrylic polymers for instant cooling without bulk or slime, making it comfortable to wear under hard hats. It fits most hard hats and safety helmets, easily and securely attaching to the suspension with 2 hook-and-loop straps. Evaporative cooling technologies such as polymer crystals are a simple, effective and comfortable solution for heat-stress prevention. Similar to how sweat cools the body, evaporative technologies use an external water source to draw heat away - helping to regulate body temperature while providing cool relief. When activated, this cooling hard hat pad is comfortable and refreshing for even the hottest days of the year.