Pure USA water is used because pound for pound, water is a more efficient coolant than gel when frozen and thawing. The vest insulates the ice from the ambient air (so it can do its job to remove heat from the body core) with a lightweight layer of neoprene. The outer layer has a ripstop fabric to provide extra strength. At less than 1" thinck, the vest allows for maximum mobility and flexibility. Each vest is outfitted with three re-freezable, removable panels that are attached with Velcro for easy replacement. Adjustable in four places, the FlexiFreeze Ice Vest has been designed to provide a snug fit for everyone from XS to 6X. The vest and panels are machine washable. Designed for a variety of uses, The FlexiFreeze Ice Vests are perfect for individuals who work in high heat environments or who are heat sensitive due to medically related reasons. The vest is also great for everyday tasks on hot days such as mowing the lawn, gardening or walking the dog.