The Kumfy Tailz Thermal Harness is a revolutionary new way to keep your dog comfortable and safe in hot or cold weather. It incorporates patented gel-pack technology, similar to hot/cold therapy packs for humans, and every harness includes a removable, reusable Kumfy Pax gel pack, which can be frozen or microwaved over and over. Simply grab a Kumfy Pax out of the freezer - or pop it in the microwave for a few seconds, and insert it into the harness pouch before walk or playtime. The Kumfy Tailz harness is specifically designed for canine physiology. Unlike people, dogs exchange most of their heat in the cardio-thoracic region (the chest and belly area). Our harness was created especially to put the thermal element directly over this region, for maximum warming/cooling benefit. Other cooling products, which focus on the neck and sides, are simply inefficient. In moderate weather, use the harness without a Kumfy Pax, and you will find it to be a thoughtfully designed, high-quality harness with innovative features; The adjustable neck provides a snug, comfortable fit on any breed. Double buckles on the belly strap mean easy-on, easy-off, and reduced strain on dogs with hip or other joint problems. The elongated back strap, with mid-body leash ring, distributes pulling force, reducing strain on the neck and throat for dogs that tug on the leash.Some veterinary literature suggests that chronic valvular, or cardiac, disease affects up to 50-Percent of mature adult dogs, often without any visible symptoms. Hot or cold weather increases a dogs cardiac stress level. Keeping your dog warm in the winter and cool in the summer reduces cardiac stress. Kumfy Tailz products are designed in the USA, in consultation with a licensed veterinarian, and are thoroughly tested. The patented Kumfy Pax UltraGel is non-toxic and reusable for years, as long as its not torn or punctured. Additional Kumfy Pax are available for purchase separately.