Our personal cooling vest maintains a comfortable 65° F temperature for up to 3 hours. The semi-solid thermal energy storage material (PCM) is designed to absorb heat generated by the wearer. A great solution for working in high humidity areas and for use under other PPE garments where evaporative products are less effective.The PCM material is set at a comfortable temperature that will not cause vasoconstriction. Vasoconstriction is a physical response to extreme cold, where the veins and arteries constrict and slow blood movement, causing the body to retain heat. 65° is comfortable and less shocking to the body's system, allowing for natural circulation.• Made in USA• Constructed from a 3 layer fabric combining hydrophilic fibers into a fibrous batting and thermally conductive core• Spot wash or hand wash only• Cooling properties can be reactivated for the life of the product; May be used over and over again• Very durable and will last multiple seasons with proper care and normal use• Perfect for use in high heat/humid areas and under protective equipment• Provides comfortable cooling up to 3 hours• Temperature set to 65°• Adjustable at shoulders and torso for snug high fit to deliver cooling to the core• Activate by placing the packs in a refrigerator or freezer for 1 hour or in a cooler with ice water for approximately 20 minutes• One size fits most: up to size 58" chest