This starter kit gets you the diffuser head and one vial of Feliway; refills are also available on Amazon. Keep in mind that if you’re introducing a new cat, you should *still* take proper precautions like keeping them separate for a while, doing smell introductions first, etc.
Promising review: “I have three cats. Male and female are brother and sister and get along well. I acquired a third cat (female) through a rescue situation several years ago. The two females have always tolerated each other, at best. We usually hear a minimum of one to two hissing matches daily with them. We also recently moved from the only house all three have ever known, and male cat begin to walk the house and cry in the middle of the night. We also noticed a strong urine smell coming from one of the boxes, even though it’s cleaned daily.
“I mentioned the crying and urine smell to the vet. He said both could be a result of stress from the move and recommended this product. I bought one for upstairs and one for downstairs. I’m shocked in the change in just a few days. First, the crying has nearly stopped and male cat is now settling in at night to sleep in bed with me. I’m not noticing the strong urine smell from the box. The conflict between the two females has also basically stopped. All three can now be found enjoying the new sun room and sitting on the couch together (even the two females). I will never go without this product in my house; I don’t know or care how, but it has resulted in three very happy cats!” —Amy B
Get it from Amazon for $22.75.