Dino,
We can put in any amount of gray hair that you'd like. I've had people request 5 strands of gray hair in a unit. But Ibetalot has a point--with that small amount you'd have to look to find the gray. And your unit is a full cap so 10 or 20 gray hairs would hardly be noticeable. But to answer your question, yes, we can do 10 or 20 strands of gray on your order.
Regards,
John
http://toplace.com/