Leather Dog Doorbells for Door Knob/Potty Training/Go Outside, Length Adjustment Copper Dog Bell, Housetraining Hanging Bell, Brown Leather Golden Bells.We designed this leather + brass bell combo dog doorbell because many customers wanted a more premium material, it's a step up from the polyester + iron bell combo on the market, which makes it not only a functional product for potty training, but also a great looking decorative piece! Fairly priced and professional quality, the bells are made of high quality copper and the inner ball is made of polished silica polymer, making the bells sound crisp