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°, and also include other non-standard angles like 60°, as required by engineering needs. Elbow materials 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, extruded elbows, cast elbows, and socket-welded elbows, etc. Other names: 90-degree elbows, right-angle bends, etc.