Grommet

A grommet is formed by integrally fitting a substantially annular flange of a grommet interior to a substantially annular flange fitting groove of a grommet exterior. The grommet exterior includes a large-diameter cylindrical portion in which the flange fitting groove is formed inside, an anti-rotation rib that projects from the flange fitting groove toward inside of the large-diameter cylindrical portion, and a first reduced-diameter cylindrical portion that is provided on an attachment side of the grommet interior to the large-diameter cylindrical portion and that has a diameter smaller than that of the large-diameter cylindrical portion. The flange of the grommet interior is provided with a notch portion into which the anti-rotation rib is fitted. Further, the first reduced-diameter cylindrical portion includes a protrusion on the outer surface thereof that indicates the position of the anti-rotation rib.