Pros: bounces well, light weighted
Cons: flimsy exterior, small edible sized bell
I originally started buying these for my birds, who LOVE this kind of bell. I tried it with the cats and they had no interest - they tend towards toys that don't have bells to begin with, but when I found a defective one in the jar that was missing a bell, I gave it to the cats. They're generally uninterested, but if we toss them and bounce them off the floor, Kismet will chase occasionally. Since that's a better reaction than complete indifference, whenever the birds break a ball, I just take the bell out and give the shell to the cats.
Because they are so flimsy, the plastic exterior breaks easily. If cats are rough or pounce on one, or if a person steps on one, it's pretty much done. When the plastic does break, if cats are left unattended, I would be afraid of curious cats who like to mouth on things accidentally swallowing the bell. It's very small and can easily be inhaled.
Cats who like to bat around small and light things may enjoy this. It doesn't take much force or effort to get one moving, but the same applies to accidentally breaking it.