In my opinion black is the easiest and I`ve never even thought about hair `size`--as long as the density and style was ok for me, I was a happy camper. My hair is some shade of brown and when I was in topper-land I found 1b was a reasonably good match before the system hair began to oxidise over time...then it was a case of coloring it and `sweating` over how the blend would look..... I guess black can be `deeper` on some people, but in my opinion, if wearing a topper and your growing hair is black, you`ll have a far easier time......just my 2-cents worth anyway ! Paul.