Cool Medics M1774F-NB-LG Unisex Zipper Front Cooling Vest. Navy Blue, Large Cools up to 6 hours at 98 degrees Lowers Temperature on the inside of the Vest by 20 Degrees Light weight and won't get your clothing wet Great for cooling down firefighters coming off fire lines, construction workers, flight line personnel, where ever heat can effect how you work or play Reusable, immerse in water (10-30 seconds) to activate the cooling process