FELIWAY Diffusers help your cat to feel secure and happy, even in different surroundings or changed situations. When a cat feels happy and safe in its environment, it deposits pheromone (scent) marks on furniture or other prominent objects. These marks convey a message of well-being and a feeling of safety. FELIWAY mimics the cat’s natural facial pheromones to create a state of familiarity and security in the cat's local environment. FELIWAY is available as a diffuser and as a spray and can be used in the following situations: To make your cat feel safe and secureTo calm your cat if it is showing symptoms of stressTo reduce stress when there is disruption to your cat’s environmentTo help integrate multi-cat households WHICH IS REFILL IS RIGHT FOR MY FELIWAY DIFFUSER? . The top of the packaging indicates which diffuser and refill go together.