The McAlpine T12 1½" x 1¼" BSP Coupling is a plumbing fitting used to connect a 1½ inch pipe to a 1¼ inch BSP (British Standard Pipe) fitting. The "T12" in the description refers to the specific model of the coupling, which is manufactured by McAlpine, a UK-based company that specializes in plumbing and drainage products. The coupling is designed with one end that fits a 1½ inch pipe and the other end with a 1¼ inch BSP thread. The BSP thread is a type of threading used in the UK for connecting pipes and fittings. The coupling is typically used to connect two pipes of different sizes in a plumbing system. Overall, this type of coupling is commonly used in plumbing applications where a secure, leak-free connection is required. The McAlpine T12 1½" x 1¼" BSP Coupling is made from high-quality materials and is designed to provide reliable performance over an extended period of time.