The Dog Cooling Vest from Ruffwear helps your dog beat the warmth. simply soak the Swamp Cooler in cold water, wring it out and fasten around your dog. phase transition cooling exchanges the warmth with the coolness of the stored water within the coat. The powdery vest keeps the sun off your dog's back for extra heat relief. Rewet the vest pro re nata as water evaporates to recharge the cooling action.