In piping systems, elbows are pipe fittings used to change the direction of the pipeline. They are commonly available in 45°, 90°, and 180° angles, and also include other non-standard angles like 60° as needed for engineering purposes. 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 fusion connection, threaded connection, and socket-weld connection, etc. They can be categorized according to production processes as: welded elbows, stamping elbows, extruded elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.