LOUD ENOUGH: 7 extra large 1.5" metal dog doorbell and metal inner ball, make clear loud ringing sound, easily audible from other room even when dog softly touches it. . DOG EASY LEARN: After simple training, most dogs are able to learn to touch the bells in about one day and fully learned to hit them to go outside or potty next week. . LENGTH ADJUSTABLE: Two snaps design for tighten the dog training bell into different belt length, makes it universal for most doorknob height, big dog, small puppy dog. . STRONG BELL METAL: To avoid pup chew or bend the dog training bell apparently, avoid the small metal ball go out of the potty bells, our dog bell use super strong metal. . EFFICIENT COMMUNICATION: Using dog door bell have been taken as an easier, fun and a win-win way for dog to talk with you instead of barking, scratching. .