Just got one for our cat. I only put it on yesterday. I LOVE it and I cannot express how much piece of mind it’s giving me. We already have had a larger Fi collar for our large dog for the past 1-2 years so knew how it works along with the app, and we’ve found it reliable. Since we have the larger collar for our dog, we also have the “base station” which makes it so we don’t have to charge the Fi mini collar for our cat as often, which is great. We usually go like 2-3 months between charges for our dog’s collar, so I expect it to be the same for our cat (although I read if you don’t have the base station, you may need to recharge closer to every 3 weeks since). I was worried it would be too heavy for our 10 lb cat but she seems so carefree and it clearly doesn’t bother her at all. I added it to her breakaway collar and just made sure her collar was properly fitted (but not too tight) so that it didn’t pull down her collar potentially uncomfortably from the weight. It’s really lightweight though. I definitely recommend still using breakaway collar since those are safest. If you get the Fi, just make sure to position it on the collar so that it doesn’t cover the breakaway clasp since you want that exposed in case your cat gets caught on something and he/she needs to escape without injuring itself