(Sergeant's) Refill unit for the Sentry Calming Diffuser. Releases Good Behavior pheromones into your home to provide cats with calming sensations. Pheromone technology has been proven to modify stress-related bad behavior such as inappropriate marking, excessive meowing, and scratching. Refill unit for the Sentry Calming Diffuser lasts up to 30 days. Lavender chamomile fragrance.