Why Chinese Companies are selling the hair in Different Grade like "5A, 6A, 7A, 8A, 9A, 10A, 15A "? What does this grade mean for?
Grade of hair determine the quality of silicon and other chemicals which make the hair looks silky and beautiful, but harmful for human health.

Why there is no Philippines, American, Canadian, European, or Mexican hair?
Because there is precisely no hair donor or hair factory, only hair donor is in South India due to the part of religious belief, donate hair to temple.