In piping systems, elbows are fittings used to change the direction of the pipeline. By angle, there are three commonly used types: 45°, 90°, and 180°, as well as other non-standard angles like 60° based on engineering requirements. 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 (the most common method), flange connection, hot melt connection, electric melt connection, threaded connection, and sleeve connection, etc. They can be categorized by production process into: welded elbows, stamped elbows, extruded elbows, cast elbows, and socket welding elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.