Synthetic hair makes the best gray.

Human gray can appear yellow either immediately or over a period of time, because the donor was probably young with dark hair.

Natural gray donor hair has become virtually inpossible to obtain.

Yak hair is very bright white and shiny and is not strong, so it can break and shed.

For an all-gray or high percentage gray unit we can mix a blend of all three gray types upon request, but all synthetic looks very good.

Exception: Ultra violet light (blacklight). If you frequent night clubs, halloween parties etc where UV is the only light, then synthetic gray hair will glow brightly. So if your hairpiece is on the top and your real hair is at the back and sides, you will see where the hairpiece ends and the real hair below will appear dark by comparison.