The Phidgets #25 Chain Sprocket w/ 12mm Bore & 18 Teeth is crafted from hardened steel, designed for compatibility with a quarter-inch roller chain. It features a 12mm bore equipped with a keyway, ensuring a secure fit onto a 12mm shaft. The sprocket is engineered to provide a robust connection through its 4mm keyway and is secured with two 2mm hex screws, making it suitable for use with #25 size chains.