Filler neck

A filler neck, comprising:

• a neck body made from resin, having an upstream end, a fuel supply opening opened at the upstream end, the fuel supply opening being opened and closed by a fuel cap, a downstream end communicating with a fuel tank, an outer peripheral surface, an inner peripheral surface, and a flange disposed on the outer peripheral surface and being fixed to a vehicle-side member;
• a retainer made of metal, having an engagement portion and an outer peripheral surface, the engagement portion engaged with the neck body, and fastened to the fuel cap;
• and
• a sealing unit securing a sealing property between the neck body and the retainer, and disposed between the inner peripheral surface of the neck body and the outer peripheral surface of the retainer;
• the engagement portion of the retainer and the sealing unit being disposed closer to the fuel tank than the flange of the neck body.