Hi Conor,
Sorry I never clicked the link. I presumed you meant interior ones...
I had a problem with this (tho maybe it wasn't necessary, going by James's reply !!)
I bought the stainless return line from DMCH. I then realised I needed the "fir tree" to go onto the bush. I got this part from Ed. I expected them to be the same thread. (well, its not unreasonable, is it??)
No joy....
I googled the name on the nut supplied with the DMCH line. I could get a fitting, but no, they couldn't supply a hose barb to mate to it. I was a bit wary as this really needs to seal fuel at a reasonably high pressure. Maybe I was being over-cautious (I wanted a guarentee that the parts I fitted would seal!)
In the end, I used the stainless hard line, ditched the nut, and ordered:
AN -6 (AN6) STRAIGHT Male To 5/16" (8mm) Tube Adapter
and
AN -6 (AN6) STRAIGHT to 8mm 5/16" Barb Hose Fitting
from torques.co.uk
Links-->
http://www.ebay.co.uk/itm/6-AN6-STRAIGH ... 27bb766698and
http://www.ebay.co.uk/itm/6-AN6-STRAIGH ... 27c83c581bNot that cheap, but I got a pressure- and fuel- rated solution which connected my hard line to the flexi hose.
Cheers
a