To increase the bending load generating the separation of an adhesive face between a core member and a metal fitting for mounting, to improve the workability, and to save labor for the work, by forming a recess on a given position of an opposite face of an inner peripheral face of a fitting mounting hole part, and an outer peripheral face of a core member, and mounting an elastic body on the recess, when the metal fitting is mounted on an edge part of the core member.

In a case when a metal fitting 4 for mounting is mounted on an edge part of a core member 1, a recess 2 is formed on an outer peripheral face of the core member 1 opposite to an inner peripheral face of an opening of a core member insertion hole of the metal fitting 4. An inner edge part in an axial direction, of an elastic body 3 mounted on the recess 2, is located on a position of an edge part in an axial direction, of the metal fitting 4, when the metal fitting 4 is mounted on the edge part of the core member 1. As the result of the same, the bending stress applied to the core member 1, can be effectively reduced by the sliding between the core member 1 and the metal fitting 4 generated as the action of the elastic body 3, and the labor or the like for mounting the metal fitting 4 to the edge part of the core member 1 can be reduced.