In piping systems, elbows are fittings used to change the direction of the pipeline. They come in three common angles: 45°, 90°, and 180°, with additional non-standard angles like 60° available based on engineering requirements. 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, mandrel-formed elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.