10 or 12
Again, it has been a while, but IIRC, Navtec sizes the cylinders based on wire or rod size (dia.). On their sizing chart, you give them your backstay dia, and they can tell you the proper size. The 38 should have the 12, but some of the 38-er's out there who recently installed them can tell you for sure.
If we are talking the old 32, or even the 36 RH-it may well be a 10.
Either way, at least for BS adjusters, it is a function of rod or wire dia.
Hope this helps,
S