In piping systems, elbows are fittings used to change the direction of the pipeline. Commonly available in 45°, 90°, and 180° angles, additional non-standard angles such as 60° may also be 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.

Connection methods to pipes include: direct welding (common method), flange connection, hot melt connection, electric melt connection, threaded connection, and sleeve connection, etc. Production processes can be categorized as: welded elbows, stamped elbows, expanded elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.