In piping systems, elbows are pipe fittings used to change the direction of the pipeline. By angle, there are three commonly used types: 45°, 90°, and 180° elbows, along with other non-standard angles like 60° as required by engineering. The 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 (the most 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, expanded elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.