Are these kitties also microchipped? That would be something handy if you don't have a collar for them but try another type of collar, I got my cats suede like collars and they are fine but then again they were fine with the nylon ones too. Since they may go out, you can try breakaway collars too so if it gets stuck they can break away from the collar. Trim the kittens nails so it won't get caught so easily on the collar also but hopefully the kitty will get used to the collar b/c you definitely want one on her if she will be going outside. (((=