Comfort Zone Multi-Cat refills pair with all Comfort Zone cat calming diffusers. Each refill provides up to 30 days of continuous calming benefits. The drug-free formula mimics a cat’s natural pheromones to let them know the area is safe and familiar which helps reduce multi-cat tension and conflict. These behaviors can include swatting, scratching, biting, fighting, hissing, growling, spitting, screaming, non-playful staring, stalking, chasing, and blocking.