Question: what is the difference between dr and sdr?
Answer: What is the difference between DR and SDR? The terms "dimension ratio" and "standard dimension ratio" are widely used in the PVC pipe industry. ... Even though the terms DR and SDR are synonymous, one minor difference between them is that SDR refers only to a particular series of numbers, i.e., 51, 41, 32.5, 26, 21, etc.