What is the attachment shown in the provided figure?

The attachment referred to in the question is identified as a flange, which is a type of mechanical component that is used to connect two pipes or other equipment together. Flanges provide a secure connection that allows for easy disassembly and maintenance of piping systems. They are typically flat with holes drilled for bolts around the perimeter to allow for bolting to another flange on a pipe or other equipment.

Flanges serve several important functions in pipefitting. They help to ensure a leak-proof seal when two pieces of pipe or fittings are joined, and they can accommodate thermal expansion and contraction of the materials involved. Additionally, flanges can be made from various materials, including metal and plastic, making them suitable for diverse applications in plumbing, heating, and industrial processes.

In contrast, other options such as reducers, couplings, and elbows serve different purposes. A reducer is used to connect pipes of different diameters, a coupling allows for joining two pipes of the same diameter, and an elbow is designed to change the direction of flow in a piping system. Therefore, identifying the correct function of a flange differentiates it from these other components in pipefitting.