I hope you are well.
There positive and negatives to both human gray and synthetic gray.
However, at 14 inches of length your only option would be synthetic or high heat synthetic gray. We are unable to provide human gray hair for lengths over 8 inches.
High heat synthetic will be consistent in color from order to order, and can be used to style the hair with temperatures up to 280 degrees.
If you would like to discuss this in further detail, with your specifications please contact us at 1-800-424-7436 and a hair replacement consultant would be happy to help you.
I hope you have a nice day.
Justine | Hair Replacement Consultant | firstname.lastname@example.org