The HeatShield II Cooling Vest goes over the head and has Velcro on the sides to accommodate up to a 52-inch chest. This is the only cooling safety vest that has a patented system for removing moisture under the vest via condensation. The HeatShield comes with one layer of quilted cooling inserts which provide around two hours of cooling. You can also add another cooling layer on top of the first with Velcro to extend the cooling period to over four hours. Extra layers for our cooling vest are available in our accessories section. We recommend this body cooling vest for our FreezerSystem.