We bought the Diffuser and this 2 pack refill at the same time. We have not used the refill yet, but here is the review that I gave the Diffuser: Don’t let the price scare you, because this is an excellent product. At least I think it is… We brought 2 new kittens into our home with a 5 year old cat already the queen of the house. We plugged this in the day we brought the 2 kittens home and have had positive results. We get a few hisses from the 5 year old to the kittens once in awhile, but nothing much. I also bought the spray and sprayed it in the room that we slowly introduced the kittens to the older cat in. So far so good. My daughter says she smells a faint odor, but no one else in the house can. I priced this item in several pet stores and it was double the price in the store!

Works very well with our cats. We have two cats that have had to adjust to apartment living from previously being inside-outside kitties with a house. One cat in particular was my "hunter" and we were concerned that she would reject being stuck in an apartment 24/7, but with comfort zone, she has mellowed out significantly. She’s playing with and cleaning our other cat on a regular basis. Both cats are really laid back now and are enjoying their new home. I’m pretty impressed.

I’ve had the diffuser and refills for about 5 months. It definitely works on the stressed cat – he gets less UTIs and eye infections now. Poor guy would get an infection every time we would go away on vacation or when we would get new furniture due to stress. However, it did not work on our aggressive cat, who urine marked everywhere 🙁