FELIWAY® CLASSIC Diffuser Refill for use with FELIWAY® CLASSIC Diffuser device (132114), sold separately. FELIWAY® CLASSIC Refills and Diffusers (sold separately) are designed to provide constant comfort and reassurance for cats. Each refill lasts up to 30 days. FELIWAY® CLASSIC is a synthetic copy of the feline facial pheromone cats use to mark their territory as safe and familiar. It is clinically proven to help reassure cats and control unwanted behaviours such as urine marking and vertical scratching.