This is a good and debatable topic but we will go straight to the point. Hair grades do not mean anything. There is no official grading system. Hair that used to be called 5A 3 years ago is now called 8A by the same vendors.
Why do I use hair grades?
I use hair grades to show a distinction between qualities I sell. For my brand Chandra Hair for example, I use them to show that my 8A quality is lower than my 9A Hair which is better quality overall. I could have called it 5A or 10A to be honest, it does not really matter! Right now, the terms 8A and 9A are hot so I use them to keep in line with the competition but at least I am open and honest about it :P