They fit very well on both my small, 8-pound cat and on my very chubby, 15-pound cat. They are cute and reflective, but not extremely sturdy. One of my boys has his fluffy from scratching at it--but it did not break, so that is much better than I have had with some brands! If your kitty likes to scratch at their collar, they may get rid of the reflective parts, but it is not likely to break through. They do easily snap open with enough tugging, but not excessively easy so that the kitty can just pop it off (which has also been a problem with some other brands).