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° elbows. Additionally, according to engineering requirements, other non-standard angle elbows, such as 60°, are also included. Elbow materials include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

Connection methods with pipes include: direct welding (commonly used), flange connection, hot melt connection, electric melt connection, threaded connection, and socket weld connection, etc. They can be classified according to production process into: welded elbows, forged elbows, expanded elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.