Fuel line diameter from fuel filter

Hi all in the process of relocating my fuel filter to the bulkhead as the previous owner left it just hanging in the engine bay after the conversion soo I need some new fuel pipe as it's way too short ATM to do anything with. Anybody no what diameter pipe I will need from the fuel filter to pump (the hard small plastic pipe) etc
Thanks in advance

6mm internal diameter
Just so happens I measured mine on friday

Thanks you sir!
Lovely fast response

Just a quick note as an addition to the job you have in hand. If you're using the original defender 300tdi air filter, a bulkhead-mounted fuel filter will be too long and it will foul the air filter hose. After lots of head scratching I sourced a shorter fuel filter to fit the Bosch-type fuel filter housing. The one used on the Citroen Xsara is a perfect fit (30mm shorter than the Land Rover type)