A234 WPB pipe elbows

An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction, usually a 90° or 45° angle, though 22.5° elbows are also made.
The ends may be machined for butt welding, threaded (usually female), or socketed, etc.
When the two ends differ in size, the fitting is called a reducing elbow or reducer elbow.