The Canine Quick Wrap maximizes the use of air flow and phase change material. The most important place to cool or warm a dog is on the underbelly, where all the blood is passing through the heart and body cavity. Use alone, or with phasechange gel pack #1 to increase cooling Please monitor your dog's core temperature. Small 11.5" long, fits dogs 12-20 lbs like Shih Tzu, Jack Russell. Medium 14.5 " long, fits 22-35 lbs. Large 19.5" long fits dogs 36-45 lbs. Large 46 and up like Doberman.