A plastic sleeve is applied to a pole of varying cross-sectional area. It is preferable that the concentration of Al and the concentration of Ti satisfy the following relations: \u22675\xd71018cm3; and 0. A disk drive base includes inner and outer sides. The control logic is coupled to the plurality of external lines and the command buffer. Base body and adhesion body are coextruded. The encryption circuit 11 coordinates with the terminal apparatus to perform a mutual authentication.