I have been looking for this exact product for a while because I have a cat who is a hunter and I don’t mind if she catches mice and voles, but I do mind when she catches the pretty birds. There are two bells that are very heavy duty, but small with a clip that is also heavy duty that connects to the cat collar. They are each about the size of a pea, and I can definitely hear them better than the one that came with the cat collar. I just let her outside and hopefully it will be loud enough to give the birds a little bit of a better chance of evading my kitties hunter skills. It’s very sturdy so I think it will stay on the collar well. I’m going to order a couple more to have on hand because at some point cats lose their collars and I want to have a spare.