LARGE ENOUGH: 7pcs extra large 1.5 inch metal dog doorbell with metal inner ball, makes a clear and loud chime that can be easily heard from other rooms even if the dog touches it lightly. EASY TO LEARN FOR DOGS: With simple training, most dogs can learn to touch the bell in about 24 hours and fully learn to bang their out or potty by the next week. Adjustable Length: Two snap buttons are designed to tighten the dog training bell to different leash lengths, making it suitable for most doorknob heights, large dogs, small dogs. STURDY METAL BELL: To avoid the puppy visibly chewing or bending the dog training bell, and the small metal balls falling out of the potty bell, our dog bells use super strong metal. Efficient Communication: Using a dog doorbell has been seen as an easier, fun and win-win way to let your dog talk to you instead of barking, scratching.