In piping systems, elbows are fittings used to change the direction of the pipeline. They come in three commonly used angles: 45°, 90°, and 180°. Additionally, elbows with other non-standard angles, such as 60°, are included based on engineering requirements. The materials for elbows include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

Connection methods to pipes include: direct welding (common method), flange connection, hot melt connection, electric melt connection, threaded connection, and socket-weld connection, etc. Categorized by production process, they are: welded elbows, stamped elbows, expansion elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.