The elbow is used when a pipe changes direction. Elbows can turn up, turn down, turn left, right, or any angle in between. The long radius (L/R) elbows denote elbows with the center-to-end dimension of 1.5D radius which equals to 1.5 x NPS in inch unit. The standard long radius elbows can be further classified as 90° and 45° according to the angle of the flow-direction change.