On weight, since this is where cats and dogs genuinely differ and the listings blur it.
A tracker sized for a dog is a meaningful load on a cat, and the problem is not only the mass. A heavier unit swings, catches on things, and sits badly on a lightweight collar, which is the thing that makes a cat work at the collar until it comes off. The tracker you lose is not the one that failed, it is the one she removed in a hedge on day nine.
What matters in practice:
- Weigh the whole assembly, tracker plus collar plus any attachment, not the figure on the box. The mounting hardware is often a surprising share of it.
- The collar has to be a proper safety-release type for a cat that goes outdoors and climbs. That is not negotiable, and it means anything on it will occasionally be lost with the collar — so buy on the assumption that you will replace it at least once, and check whether spare collars are sold separately and at what price.
- Check the profile, not just the grams. A flat unit that sits against the neck behaves completely differently from a chunky one that hangs and swings, at the same weight.
A practical trick before you spend anything: tape a coin or two of roughly the right mass to her existing collar for a week. If she is at it constantly or the collar keeps coming off, you have learned that for nothing.