a lid of a fuel tank comprises a lid body constructed of a molded plastic and shaped and sized to be put in an opening formed in a wall of the fuel tank . the lid body has a first portion that is exposed to an outside of the fuel tank when the lid is put in the opening of the wall and a second portion that is exposed to an interior of the fuel tank when the lid is put in the opening of the wall . at least one of the first and second portions has a flat surface for mounting thereon external parts . the lid further comprises a through passage that extends in and through the lid body between the first and second portions . the through passage includes a first passage part terminating at the first portion , a second passage part terminating at the second portion , and a third passage part extending between the first and second passage parts to connect the same . the first and second passage parts are offset in a direction parallel with the flat surface .