Don't get me wrong, this is actually a great quality item and well made.... it just not for every cat. we got a kitten Sept 2014, he was small and then got really sick and I was put on a last minute, 7 month business trip. So he didn't get introduced to our other two cats until July. our oldest cat, Felix, started plucking the fur out of his tail and then he started obsessively cleaning himself when he never really cleaned himself before. The vet diagnosed him with an anxiety disorder and suggested this or plug-in diffusers. We got the calming plug ins first, but he just seemed tired and zombie-like, so I was hoping the Thundershirt would help. he likes to cuddle, to be wrapped in towels/blankets, and extra heat, so I assumed this would be perfect. We first put it on him and he did the flop over that the instructions mentioned could happen. Its a new and weird sensation, so its going to happen. we started playing with Felix, but the other two kept sniffing him, so we took him out of the room. He got treats and scratches, some playing and was allowed to explore the rest of the house. He seemed to be building confidence and was more outgoing than he's been in a long time. we took him back to the cats room (our cats have their own room, a small master bedroom size), and the other two came over to sniff the shirt again - poor Felix's head and tail went down lower then it was before the shirt - I didn't know a cat could even be self-conscious. My husband and I played with them for another hour to get everyone used to the shirt and rebuild confidence and bonds. we left it on him for the rest of the night. He is used to wearing it, but doesn't like it and its nothing new for the other two cats Pros: -other reviews for this item (the large offered on Amazon) said this was T-shirt material, its NOT. it is like a thick track suit. a lot heavier than a t-shirt, but lighter weight than a sweat shirt. Its not going to get snagged if he scratches at it. It is breathable too - I've stuck my hand between the shirt and cat to make sure he wasn't over heating (this also ties in with a con below) -easy to figure out with our without instructions -The instructions - it was very helpful to expect the flop and ways to coax the cat into seeing the shirt positively Cons: - sizing - I went off girth around the chest. I measured and checked with the size chart. He was supposed to be a medium. there is exposed Velcro when Felix is wearing the shirt because he's a little chunky (its the soft side of the velcro so he isn't scratching himself or collecting lint/etc) He isn't a huge cat, but he isn't small. when the shirt is pulled to just behind his front legs, his back legs wrinkle the shirt (its too long for him). -the front Velcro- if I tighten it enough to keep the shirt al the way forward, there's excess that he pulls at - hes gotten very good at undoing the front Velcro. if I line the Velcro up so that there isn't an excess for him to grab, it doesn't get as tight at the cat in the displasy picture and the shirt slides back. He's also gotten his jaw stuck in it. - When Felix sleeps in a ball, the Velcro crumples and it looks like the back gets stretched and stays stretched when he gets up. - possibly too breathable. We keep a heater in the cat room for when my husband cranks the AC. the last couple times I turned the heater on while Felix was wearing the shirt, he sprinted to the heater and was standing on his back legs to try to get the full force of heat. the room wasn't that cold and that was out of his character. Overall, My cat doesn't like it. twice now I took his harness off to put the shirt on him and he went to the other side of the room and wouldn't come near me when he normally comes when I call. he bites at it and pulls at it. Its got great reviews, vet recommended, but, like humans, every cat is different.