PhaseCore is a non-toxic, non-flammable phase change material (PCM) made of a salt blend sealed inside of an aluminum wrapper. It changes from solid to liquid and back again depending on the surrounding temperature. PhaseCore elements are not effected by humidity and react to direct heat. Garments in a variety of styles and materials are designed to utilize the cooling effects of PhaseCore elements to reduce heat stress. Vests are available in a variety of styles and sizes.