In piping systems, elbows are fittings that change the direction of the pipe. By angle, there are three commonly used types: 45°, 90°, and 180°, along with other non-standard angles like 60° as needed for engineering purposes. The materials for elbows include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

Connection methods with pipes include: direct welding (commonly used), flange connection, hot melt connection, electric melt connection, threaded connection, and socket welding connection, etc. According to the production process, they can be divided into: welded elbows, stamped elbows, mandrel-formed elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.