In piping systems, elbows are pipe fittings used to change the direction of the pipeline. By angle, there are three commonly used types: 45°, 90°, and 180° elbows. Additionally, other non-standard angle elbows, such as 60°, are included according to engineering requirements. Elbow materials include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

Ways to connect pipes include direct welding (common method), flange connection, hot melt connection, electric melt connection, threaded connection, and socket-weld connection, etc. According to the production process, they can be categorized as: welded elbows, stamped elbows, expanded elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.