The McAlpine S12C is a 1 1/4" BSP (British Standard Pipe) female to male coupling. It is a plumbing fitting that is commonly used to join two pipes or fittings with male and female threads together.The S12C coupling is made from high-quality materials to ensure it is durable and long-lasting. It has a female BSP thread on one end and a male BSP thread on the other end, making it compatible with a wide range of other BSP fittings. The McAlpine S12C coupling is suitable for use with a range of different liquids and gases, including water, gas, and oil. It is commonly used in commercial and residential plumbing installations and can be used in a variety of different plumbing systems.