Feliway Optimum Cat Diffuser Refill, 6 count; Minimize household chaos with Feliway Optimum Cat Diffuser Refill. This diffuser refill recreates calming natural cat pheromones to remind your feline friend that he’s not a wild cat. The special Optimum formula helps prevent unwanted behaviors like scratching, urine spraying, and conflict. When used with a Feliway Optimum Plug-In Diffuser (sold separately), each refill can help bring calm to your house for up to 30 days. Simply find a spot near your furry friend’s favorite hangout not covered by a door or curtain and plug it in. You’ll love it, and so will your kitty!