Fuel pipe diameter

My fuel pipes are rotted, but only about a foot of them, maybe 2. They have been previously bodgged together by previous owners/garages.

I need to replace them or at least fix the bad part. What is the outside diameter of the fuel lines? are there 2 or 3 different diameters? Feed + Return + vent?

Is nylon ok? They are currently boddged with different bits of rubber line and hose clamps. What sort of connectors are hiding on top of the tank? (anoyed there is no acess pannel in the floor, but too lazy to make my own).

I cannot comment on diameter of fuel line but here are some photos of what you will find on the top of tank and what you'll need to remove those fuel lines. It's difficult to buy that Suzuki tool but I managed to make one out of a 10mm OD plastic tube.