shanew

As per the title, I've searched to the best of my ability but can not find the answer.
I have a leak on the hard line on the underside of the car where it comes through from under the seat. I've been told to just replace the section with some flexible fuel line and jubilee clips. Problem is I have no idea what size fuel line to buy and can't find the answer online.

Anyone advise on what to buy?

Cheers.