The Pettracer collar is a very good product. The collar itself is solidly made (unlike another "similar" product that I bought first and returned as useless). It is reasonably straightforward to set up and the app is easy to use - I am in my dotage and with a little helpful help from the Pettracer team got it working quickly. My cat - 3.7kg - wears it with no resistance at all. It was a huge reassurance to me when I first let her out after rescuing her in December. She is a wild thing and I feared she'd disappear. The system lets me follow her movements and be reassured that she's not too far away - she's been about 1/2 km away at most so far - and always managed to find her way home. The Pettracer system is more expensive than others but it definitely works and I'd say is good value for money.