Abstract: A coupling structure for coupling first and second wheel pieces includes (a) a radially-positioning coupling including a radially-positioning protrusion and a radially-positioning recess, (b) a circumferentially-positioning coupling including a circumference protrusion and a circumference protrusion-receiving recess and (c) an axially-positioning coupling including an arm and a claw receiver. As a result, even eliminating welding and coupling by a bolt, it is possible to couple the first and second wheel pieces securely by a physical coupling such as fitting, engaging, inserting and press-fitting.

Abstract: A High Rigidity Wheel Rim is provided comprising a pair of axially spaced radially outward extending annular flanges, an annular well portion intermediate the flanges, and an annular bead seat portion adjacent to each flange and axially spaced from the well portion wherein each bead seat radius is no greater than about 4.5 mm.

Abstract: In construction of a racket frame provided with at least one string protector coupled to the outer peripheral surface of its head, at least one weight adjusting element is removably attached to the outer peripheral surface of the string protector for easy weight adjustment by users even after formation of a face in tension.