FELIWAY Friends Diffuser is a clinically proven solution to help cats live in harmony together at home. The diffuser works continuously to help reduce the frequency and intensity of fighting, tension and conflicts between cats in the home. Plug the diffuser and refill in right side up in an open area where your cats spend the most time. You may need multiple diffusers if your cats avoid each other. Keep plugged in continuously and replace refills every 30 days. Replace the diffuser device every 6 months. Each diffuser and refill covers up to 750 square feet. Best results are typically seen after 3 to 4 weeks of continuous use. Use only FELIWAY Refills with FELIWAY Diffusers; do not use with any other refill or device.