What is the meaning of SDR ? And Is it important to be determined?

I was hoping to find any answer to express the meaning of shring " Knowledge, Experience" .

But i'll briefly explain the importance of SDR Expression.

 SDR means  "Standard Dimension Ratio" - SDR - method of rating pressure piping. The SDR is the ratio of pipe diameter to wall thickness and the SDR can be expressed as

SDR = D / s         (1)

where

D = pipe outside diameter (mm)

s = pipe wall thickness (mm)  

A SDR11 means that the outside diameter - D - of the pipe is eleven times the thickness - s - of the wall.

• with a high SDR ratio the pipe wall is thin compared to the pipe diameter
• with a low SDR ratio the pipe wall is thick compared to the pipe diameter

As a consequence a high SDR pipe has a low-pressure rating and low SDR pipe has a high-pressure rating.