I personally don't like collars on cats, I used to work as a vet tech and some of the injuries caused by cat collars were horrendous!, they need to be fairly loose and cats often get a foot inside the collar and if the leg doesn't break the leg can get stuck right up to the 'armpit' and if the cat doesn't get freed by a human the collar then can proceed to cut into the skin, if you have had your kitten micro chipped it shouldn't need to wear a collar as well, and a kitten this young rarely ventures fair away from home.