When attempt is made to insert a fitting-shaft section into a fitting-hole section in a state where phases of the fitting-shaft section of a spring-screw and the fitting-hole section of an adapter about a central-axis line of a spool-body are not matched, shaft-section-side inclined-surfaces formed at shaft-section-side protrusions abut to hole-section-side inclined-surfaces formed at hole-section-side protrusions, so the shaft-section-side inclined-surfaces press the hole-section-side inclined-surfaces in such a direction inclined in a pull-out direction to a projecting-direction of a shaft-section body from a flange section. The adapter having received a pressing force generated by this pressing at the hole-section-side inclined-surfaces has rotated in the pull-out direction, and then the phases of the fitting-hole section and the fitting-shaft section have aligned about the central-axis line of the spool-body, each shaft-section-side protrusion intrudes into a gap between the hole-section-side protrusions adjacent to each other, and the fitting-shaft section fits into the fitting-hole section.