Color: Black Material: Nylon + Iron Size:Band Length:2.5*96cm, Bell Diameter:3.8cm Package included:2 x Pet bell rope 1.Useful and Simple Pet Doorbell: These dog bells can be easily hung on the door knob or handle. Without scratching or barking, this bell will know when your puppy needs the toilet. 2.High quality puppy doorbell: The dog doorbells are made of strong nylon band and durable iron bell, bite-proof and good for long time use. Besides, this adjustable door bell strap has 7 bells, it can be easily touched by most dogs. 3.Audible Sound: The voice of the dog doorbell is loud but not hard, can be heard within 20 meters. This way you can't hear the sounds in the same room, you don't need to worry about the dogs sneaking out, this fun dog bell will attract your attention. 4.AdjustbaleThis design provides you level of length adjustments compared to common two length bells. This allows for easy adjustment of the length to the bottom of the door or wall based on the size of your dog or the height of your door. 5.VERSATILE DESIGNYou do not have to worry about the dog doorbell string not matching your doors or knobs in type or size since these dog training bells for door are for all kinds of knobs these are the ideal bells for dogs to ring to go outside.