:confused:  To serve a fast-flight string, which size serving should i use? .026?, or ?
                      thank you.

How many strands? Is your string orignal fastflight, or another material that your using the generic term fastflight for? What arrow nocks are you using?

Rod.
Please forgive my ignorence here.
The sring is dyneema/spectra flemish string. How many strands? I have no idea.
I think my nocks are called "X nocks"?

No problem....but its impossible to recommend a serving diameter, without knowing strand count and material as the different material vary in strand diameter....might get you in the ballpark, knowing strand count..........unstring that bow and get to counting!  :D

Hey Rod.
I come up with 18 strands.

help please  

Im guessing a string with 18 strands may in fact be Fastflight or a simlar strand diameter material such as 8125...

I'd go with .021 or.022 diameter serving with the Xnocks.

Thanks for your help Rod, i appreciate it.    
Steve.

Presently, I'm using a 16 strand FF string, and using .018 FF serving material.  I would assume, for others, how you like your arrow nocks to fit.

David