KewlFit Performance Enhancing Vest, Black, X-Large/XX-Large Front zipper with mesh ventilation panels and adjustable side gusset for optimal fit on all body shapes Cotton material provides comfort and washability after workouts Hybrid Cooling, Uses both Evaporative Cooling HyperKewl Fabric and Removable Phase Change Cooling Packs Include one (1) set ofCool Pax Phase Change Cooling Military Vest Inserts (7065 w/velcro) and insulated Kewler Bag Temperature has been shown to maximize the gradient to reduce heat storage without invoking any vasoconstriction response or shiver reaction