In piping systems, elbows are fittings used to change the direction of the pipeline. Commonly, there are three types based on angles: 45°, 90°, and 180° elbows. Additionally, elbows with other non-standard angles, such as 60°, are included based on engineering requirements. Materials for elbows 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 welding connection, etc. They can be categorized by production process into: welded elbows, stamped elbows, mandrel-formed elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.