I used them on some of my cats years ago and they always managed to remove them. They would just bite the cap and tug on it until it popped off. It wasn't worth the money for my past cats, but I would probably use them again if need be. My cats are not scratchers, they will occasionally scratch the chair, but I don't mind. Mine are all grown up now, so they are out of their climb the curtain stages. (*thanks gawd*)!