To solve the problems of conventional techniques wherein, while problems regarding appearance are solved because a locking part for a shaft tube body and a closing member is formed in the inside diameter part of a shaft tube and while the locking part prevents the closing member from being disconnected from the shaft tube when the shaft tube body is pressed from its outer peripheral surface toward its inside diameter side, the trouble of the closing member being disconnected from the shaft tube body could happen if the shaft tube body is pressed from the inside diameter side toward its outer peripheral surface, because sufficient locking cannot be achieved as the locking part of the closing member will collapse inward along a slope of the locking part with respect to the shaft tube body, and wherein, if a window hole in the shaft tube body makes contact with the closing member during use, a corner of one of the window hole and the closing member is rubbed, causing a rubbing sound.

In the shaft tube, a window hole is provided in a side face of a shaft tube body and a window member is attached to the window hole. A plurality of projections and a plurality of locking parts that fit the projections are formed at the mating parts of the window hole and the window member. The window member is provided with a notched part.