The fuel line comes in the following sizes

Just choose the option you require and then the length you require.   

Diameter  -  2.mm i/d x 3.5mm o/d

 Diameter  -  2.5mm i/d x 4.5mm o/d

Diameter  -  2.5mm i/d x 5.0mm o/d

Diameter  -  3.0mm i/d x 5.0mm o/d

Please note this fuel line is suitable for standard fuels but not fuels with high ethanol content.