In pipeline systems, elbows are fittings used to change the direction of the pipeline. By angle, there are three commonly used types: 45°, 90°, and 180°, along with other non-standard angles like 60° as needed for engineering purposes. Elbows are available in materials such as cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

Ways to connect pipes include direct welding (commonly used), flange connection, hot melt connection, electric melt connection, threaded connection, and socket welding connection, etc. They can be categorized by production process as: welded elbows, stamped elbows, extruded elbows, cast elbows, and socket weld elbows, etc. Other names: 90-degree elbows, right-angle bends, etc.