An upright portion of an inner band section is inserted into an elongated hole in an outer band section, and a tab stopper of the outer band section is inserted in a cutout hole on the base end side of the upright portion. As a result, a band member is temporarily held in a ring shape. When an inner and an outer pulling claw are pulled together, a fixing hole in the outer band section engages a fixing claw of the inner band section and the tab stopper engages a stopper receiving hole. This results in the band member being fixed with its diameter reduced.