Feliway Friends is a synthetic, odorless copy of the cat appeasing pheromone (CAP), naturally produced by female cats after giving birth. This pheromone helps the kittens feel safe, and it helps develop a bond and a harmonious environment between them and their mother. Moreover, Feliway Friends Diffuser replicates this calming effect in adult cats. Use Feliway Friends Refill every month to continue to create harmony in your home, and avoid tensions between your cats living together. Note: This is the refill only for the Feliway Friends Diffuser, diffuser NOT included.