GROMMET

In the grommet, it is assumed that a point at a leading end position of the extension portion is a point A, and a point at a position furthest from the point A as seen in the insertion direction in a leading end region of the fitting portion in the insertion direction is a point B. It is assumed that a width of the through hole in a cross section that is parallel with the insertion direction and passes through the point A and the point B when the fitting portion is fitted to the through hole is a hole width W. At this time, a total of a linear distance L between the point A and the point B and a thickness T of the seal lip is larger than the hole width W.