McNash,
When we order 40% gray and above the factory only offers real human hair since using that much synthetic gray would not act like natural hair. In fact, we only use synthetic gray when a customer asks for it--regardless of percentage. When you get into gray percentages of 40% and upwards the only way to go is natural. Blending that much synthetic gray with real human hair is a real mis-match. They have different characteristics and behave differently when the wind blows through you hair. Not to mention anything of how synthetic reflects the natural sunlight differently than real human hair. Synthetic gray in small amounts is o.k.--you won't notice the difference. Back2Natural will color the gray.
Regards,
John