Reducers: A reducer is a kind of pipe fitting used in process piping that reduces the pipe size from a larger bore to a smaller bore (inner diameter). A reducer allows for a change in pipe size to meet hydraulic flow requirements of the system or to adapt to existing piping of a different size.

Elbows: An elbow is installed between two lengths of pipe (or tubing) to allow a change of direction, usually a 90° or 45° angle; 22.5° elbows are also available. The ends may be machined for butt welding, threaded (usually female), or socketed. When the ends differ in size, it is known as a reducing (or reducer) elbow.