For dogs; A natural way to reduce anxiety, aggression, and destructive behavior; Constant delivery of natural, calming pheromones; Long-lasting ??? each collar works for 30 days; For dogs with up to 23 inch neck sizes 28 inch collar -- Nurture Calm Phero Collar Canine %5B28inches%5D. Proven to effectively treat behavior problems in dogs and cats that are caused by stress, anxiety and phobias, such as separation anxiety, travel, new environments and social interaction. Provides superior, longer-lasting delivery of pheromones than any other pheromone product and goes where the animal goes to provide round-the-clock pheromone release. This is a safe and effective first-line treatment that often eliminates the need for powerful prescription medicines. Can be used on dogs and cats of all breeds and ages and without side effects.