A grommet (1) has a central shaft (2)through which a wire harness (5) is inserted. A circular connection portion (31) is provided continuously to the periphery of the central shaft(2.) A convex cross-sectionally V-shaped ring-like lip (32) is extensibly provided to the circular connection portion (31) in the direction of the center of the central shaft. A flange portion (33) is provided continuously to the lip portion (32.) When the grommet (1) is assembled to a body panel (10,) the lip (32) of the grommet (1) is extended in the direction of the center of the central shaft (2) of the grommet (1,) thereby reducing the diameter of the lip (32.) Then, the lip(32) is inserted into the through hole (12) of the body panel (10.) Thus, a low insertion force is sufficient when the grommet is inserted thereinto. Consequently, the assemblability of the grommet (1)is enhanced.