In piping systems, elbows are fittings used to change the direction of the pipeline. Commonly available in 45°, 90°, and 180° angles, additional non-standard angles like 60° may also be included based on engineering requirements. Elbow materials 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. According to the production process, they can be categorized as: welded elbows, stamping elbows, push-fit elbows, casting elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.