ZippyPaws Cooling Vest is a high-visibility reflective vest designed for the active dog. The bright blue color and reflective stripes help keep dogs visible during hunting season, night-time walks, and in low-light conditions.Long-lasting cooling polymer crystals, which are sewn directly into the vest, absorb water and slowly evaporate to help keep dogs cool for up to 9 hours. To activate cooling features, simply soak vest in water for 5 minutes before use. Squeeze out excess water. For maximum cooling, soak in ice water before use. Lay flat to dry, do not wring.Comes in 3 sizes:-Small: 16 – 24′ in girth-Medium: 23 – 32′ in girth-Large: 30 – 40′ in girth