The McAlpine 1 3/4" X 1 1/2" Bsp Female X Bsp Male Coupling T12B is a plumbing fitting used to connect two pipes of different sizes. It has a female end with a 1 3/4" BSP (British Standard Pipe) thread and a male end with a 1 1/2" BSP thread. This coupling is made of durable and corrosion-resistant materials to ensure long-lasting performance in plumbing systems. It is easy to install and provides a secure, leak-free connection between pipes. This coupling can be used in various plumbing applications, such as in water supply systems, heating systems, and waste systems. It is available in 9 sizes and functions as a waste outlet reducer.