Best Cat Calming Choice: Optimum Cat Diffuser Refill FELIWAY Optimum calms cats better than ever. Reduces more signs of stress in various situations. Diffuser device sold separately. Safe & Vet-Recommended Trusted by vets for over 25 years. Over 14 million cats helped worldwide. Expertise in cat stress and calming innovation. More Effective & Comprehensive Supported by 25 clinical studies. 93% of owners report enhanced calming. Average satisfaction rating: 9.1/10. Works for both single-cat and multi-cat situations. Easy-to-Use Plug in where your cat spends the most time. Use an outlet free of other devices. Covers 700 sq ft and is scentless. No effect on humans or other pets. Requires 4 ft of clearance above the diffuser. The diffuser will get warm and show a green indicator light when operating. For Best Results Use with FELIWAY diffusers only. Refills last up to 30 days. Replace the diffuser every 6 months. Best results after 3-4 weeks of continuous use. Some cats show improvements within 7 days. Keep your Cats relaxed with the Optimum 30 Day Cat Diffuser Refill!