Caldwell's Pet Supply Co. Potty Bells for dogs are created with durability and style in mind. We are The Original Dog Doorbell! Our dog doorbells are made with six large silver bells, adjustable length strap and available in your choice of eight colors! Not only are our Potty Bells the best in function, they also stand out with our unique attractive dog door bell design. Potty Bells have an adjustable strap with snaps that allow you to hang them on lever-style door handles, traditional door knobs and even patio/sliding glass door handles! Our sturdy strap is made of heavy duty nylon for superior strength. Potty Bells will stand up to your dog's paws and claws. Our bells are silver-tone plated steel bells for the best durability and sound quality. No skimping on the superior materials chosen for Potty Bells by Caldwell's Pet Supply Co...ever! Note: Potty Bells should never be used outdoors. Inclement weather, air pollution, even normal weather conditions and other elements can discolor your Potty Bell strap and cause the bells to rust.