This vest has an adjustable custom fit. It is important for cooling vests to fit snug to the body for optimal cooling. This cooling vest has adjustable hook and loop straps at the chest, waist and shoulders for a snug, comfortable and customized fit. Once the cooling vest has been adjusted for size, it is easy to put on every time with the zipper-pull front. Wear the vest over clothing or discreetly underneath. The cooling vest shell is constructed of durable and machine washable 100% cotton twill. Cool58 cooling packs freeze solid at a moderate and comfortable temperature of 58° Fahrenheit, so they can be activated in a freezer, refrigerator, or even a bucket of ice water. (Please note: cooling times are estimates and will vary depending on climate, body metabolism and activity.) The vest includes four (4) Cool58 cooling pack strips. The packs fit into insulated pockets inside the cooling vest. The pockets have a comfortable all-cotton fabric to protect the skin and an insulated outer composite fabric to direct the cooling energy toward the body. Temperature may also be adjusted for comfort by increasing or decreasing the number of clothing layers beneath the vest or the number of packs used.