In piping systems, elbows are fittings that change the direction of a pipe. The three most commonly used angles are 45°, 90°, and 180°. 

Other non-standard angles, such as 60°, are also available depending on project requirements. Elbows are made from materials such as 

cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, nonferrous metals, and plastics.