"if i specify 8mm on my drawing will that be ok?"
I vote no. How about you? I'm joking.
You have given us ZERO information to help you. We have no idea what the part is, how it will be used, how it will be made, how critical this dimension is, how much it will cost, how significant failure would be, or any other inportant factors. Maybe its time you put your engineer cap on and take some responsibility for making a design decision, instead of just copying someone else's work.