1/8npt iirc.
just had a look through my Think receipts to remind myself - the FBM range is for the Racing hose (FC333 - the teflon linered stuff), which is what I used to plumb in the pressure side of the fuel lines from the reg, so you'd need an FBM1012 for that.
the HEF range is push fit, so if you have rubber hose like you say, it'll be that one you need.