I wasn't sure if they would 100% work but after using them for a couple of months I can confirm they definitely do! One of our girls is a bit sensitive to… well everything… so I thought I'd try these after the plugins not really doing much for her. I hadn't realised just how much they were working until she started spraying again the other day and I realised it was because her collar needed changing to a new one. Within 24hours of changing it to the new one she's stopped weeing on things again and she curled up in my lap all purry. Honestly so happy with these, it's nice to have our happy purry girl back.
They do absolutely stink when you first get them out but she gets used to it quickly and i'm really not concerned that they're too strong for her as we left the collar loose enough for her to get it off if needed and she never even tried.

We used these on our 2 cats for our house move. One cat is particularly timid and hides all day and only comes out for food. Since putting his collar on her she's been so much confident and is out, playing and cuddling us after 4 years of having her! I decided not to replace the collar just to test it, it's now been 5 weeks so the collar needs replacing and low and behold, she is starting to hide again… so they very clearly do work. No adverse side effects with either cat either.

After my two cats came down with some sort of viral infection that seem to after their sense of smell. There was an increase in the little one (6months) annoying the older one (7 years), when they had come to tolerate each other – even play – prior to their colds. I bought these hoping that it would calm them, and possible reset everything. When I put the collar on the kitten, there was an immediate calm, which lasted about 12-24 hours. After that, he seemed to go back to harassing the bigger cat as he had been. There was no noticeable effect on the older cat. The collars do smell of lavender, pretty strongly at first. It didn't really bother me, but if you're sensitive, beware. After a couple weeks of wearing them, you could still smell the scent if the cats were on laps, etc, but not when they walked in the room. Overall, I'd say the CAN have a calming effect, but overall, I don't think I'll both continuing with them.

This product works wonderfully—I now have two incredibly relaxed and happy cats! The collar is effective at creating a calming atmosphere, which has made a noticeable difference in their behavior. However, I’m giving it 4 stars instead of 5 because of the strong lavender scent. While I understand the scent is meant to contribute to the calming effect, it’s quite overpowering and can be a bit overwhelming for someone like me, who is slightly allergic to lavender. If you’re not sensitive to strong fragrances, this is an excellent choice for keeping your cats calm and content.

Scent last for week or 2, didn't really do anything as to ease my cat. Utter tat on Amazon!

Easy to use and works well

Ordered to help a cat who was very load and seemed stressed. It’s calmed her drastically.

The smell is so strong! Despite my better judgment (because of the smell!) I put one on my cat, I was desperate for something to help my stressed cat. I but ended up with a cat who smelt like old Auntie Maude with no obvious calming effects.
I ended up taking this off after two days as the smell didn't get any less strong and the cat no less stressed.
I am not sure why a Pheromone collar needs such a strong synthetic lavender smell.
Also of note these types of collars are not break away style, I hadn't thought of this when ordering. As my cat is an outdoor/indoor cat I feared for her safety if she got caught in a bush.
Back to the drawing board for us.