In piping systems, elbows are fittings that change the direction of the pipeline. According to the angle, there are three most commonly used types: 45 °, 90 °, and 180 °. In addition, other abnormal angle elbows such as 60 ° are also included according to engineering needs. The materials for elbows include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

The methods of connecting with pipes include direct welding (the most commonly used method) flange connection, hot melt connection, electric melt connection, threaded connection, and socket connection. According to the production process, it can be divided into welded elbows, stamped elbows, push made elbows, cast elbows, welded elbows, etc. Other names: 90 degree bend, right angle bend, etc.