Fuel line is hose that carries fuel from one location to another. The most common place for fuel line on a moped is between the gas tank and the carburetor. Usually the fuel line will connect to the gas tank at the petcock. Most mopeds use 3/16" fuel line.
In-line fuel filters are placed in the fuel line to help prevent sediment from clogging the carburetor.
Clear or transparent fuel line makes it easy to see when gas is or is not flowing to the carburetor, and this can aid in troubleshooting fuel system issues.
For information about stretching fuel line see Fuel line fitting.