SENTRY® Calming Collars use patented Good Behavior™ pheromone technology. Using a pheromone that mimics the one mother dogs produce to calm their puppies, the collars are clinically proven to reduce or eliminate stress-related behavior such as inappropriate marking, excessive barking and chewing. Collars help alleviate problem behaviors triggered by travel, thunderstorms, fireworks, being left alone and new social situations. This collar continues to release calming pheromones for your dog for 30 days. It can be used for dogs of all ages and breeds without long-term side effects. This economy 3-pack is perfect for multi-dog households.