In piping systems, elbows are fittings used to change the direction of the pipeline. They are categorized by angle, with the most common being 45°, 90°, and 180°. Additionally, elbows with other non-standard angles, such as 60°, are included according to engineering requirements. 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 sleeve connection, etc. They can be classified according to production processes into: welded elbows, stamping elbows, push-fit elbows, cast elbows, and double-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.