I used to have them for all of them, but they would either get them off, or scare me to death with getting them caught on their teeth, claws or other things. I just watch all of my cats like hawks, so that NO ONE gets outdoors without my knowledge! Luckily any of them who ever have managed to get out the door, generally FREAK OUT and come screaming back to the house like, WHAT THE HECK WAS I THINKING!!!!!!