Adaptil™ (Formerly D.A.P®) - Dog Appeasing Pheromone (D.A.P.) offers an effective way for your dog to cope with stressful situations. D.A.P. mimics the pheromone a mother dog produces to calm and reassure her puppies. This calming effect appears to work on both young and adult dogs. D.A.P. Collar stays with your dog all the time to help control stress-related behaviors, like introduction of a new puppy, going on walks, thunderstorm season, fear of traveling, puppy socialization, boarding and grooming, as well as, fireworks and gunshots. Medium/Large collar fits necks 15-25". Small collar fits necks up to 15".