<p>A receiving surface (625) for use in the supersonic welding of the welding boss (620) of an M cassette tape reel (612a) is composed of the lower surface of a ring portion (626) which is formed so as to extend annularly along the base end of a hub central portion (621) formed in the bottom surface (616a) of a lower reel (616) and also which is projected downward (in Fig. 2) by a given amount from the bottom surface (616a). That is, the receiving surface (625) is situated slightly outside in the radial direction from directly below the welding boss (620). <IMAGE></p>
