Even when fully soaked, the jacket holds the water, keeping your dog cool and dry. The jacket can be charged over and over. When winter comes, a dry jacket becomes an insulating jacket, helping to cut the cold. In addition, COOL K-9 is equipped with reflective strips to make your dog more visible at night. The yellow and red design also increases your dog’s visibility in all environments. The jacket is a year-round safety device. Hikers, bikers, walkers, runners, hunters, and dog-lovers alike have applauded COOL K-9.Submerge the jacket by placing it in a basin of water, or by adding water directly to the bag containing the jacket. Soak for 30 minutes or until fully saturated. Wash by hand, no harsh abrasives. Hang to dry when not in use. Do not freeze! Medium: 30 - 60 lbs, fits 22" - 31" Chest Size Using water absorbing, polymer crystals, sewn into supplex fabric, the evaporative process allows heat to physically transfer from the dog to the jacket, similar to our bodies own manner of cooling through perspiration. Keeping your dog cool and protected from heat exhaustion. The jacket absorbs water quickly, but releases it slowly. By submerging the jacket in water for just a few minutes, the crystals absorb enough to keep the evaporative process going for up to several days.