In piping systems, elbows are pipe 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 according to engineering requirements. Materials for elbows include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

Connection methods for pipes include: direct welding (commonly used), flange connection, hot melt connection, electric melt connection, threaded connection, and socket-weld connection, etc. Classification by production process: welded elbow, stamped elbow, expansion elbow, cast elbow, and socket-weld elbow, etc. Other names: 90-degree elbow, right-angle bend, etc.