Fittings that change direction in a piping system are called elbows. The directional change is given in degree such as 45 or 90. Long radius 90 degree elbow has the center line of elbow at 1.5 x NPS from eblow end. 3R elbow has center line at 3 x NPS from elbow end. Short Radius 90 degree elbow is same as LR90 except for the measurement between end of elbow to center line is 1 x NPS.