FELIWAY Optimum is a new, patented pheromone discovery, and is the best FELIWAY answer to help reduce the most common signs of stress in cats. It helps with more signs of stress, in more situations, and calms cats better than ever; it may help reduce scratching, urine spraying (peeing), tensions & conflicts among cats, general fears, and reactions to changes. This new discovery, backed by FFELIWAY's 25+ years of feline stress expertise, delivers advanced calming messages, helping your cats feel more comfortable at home than ever before. When surveyed, 93% of cat owners reported enhanced calming for their cats when using FELIWAY Optimum. This product contains 6 refills for the FELIWAY Optimum diffuser (diffuser head not included). FELIWAY Optimum's heated diffuser and refill provide calming pheromones continually for up to 30 days in a 700 square foot area. We recommend using an additional diffuser if the room is bigger than 700 square feet. We recommend plugging in the FELIWAY Optimum diffuser in the room where you cat spends the most time, or where conflict among your cats happen most frequently. Try not to plug the diffuser under items (e.g. shelves) or close to objects (e.g. behind curtain or doors) as this affects efficacy. We do not recommend plugging your diffuser in near your litterbox or in a hallway - while your cat may frequent these places, they likely do not spend as much time in these places as you'd think. If your litterbox is in the room where your cat spends the most time, you will want to plug your diffuser into that room. Use FELIWAY Optimum each month to create a constant calming environment. Check the diffuser and refills monthly; you'll want to replace the refill each month, and replace the diffuser head twice a year (every six months) to guarantee the best effect. Make sure to only use a FELIWAY Optimum diffuser with a FELIWAY Optimum Refill. The diffuser is not compatible with refills from other brands, and the FELIWAY Optimum vial should not be used with other diffusers. Never use a diffuser or refill of another brand with a FELIWAY product. Each FELIWAY Diffuser comes with a plug adapted to the local electric systems. Please do not use this diffuser in another country that has a different voltage or with an adapter: it may conduct serious security concerns. Make sure that your diffuser has the fitting plug for your country before plugging in.