In a motor including a chucking device for detachably holding a disk, the chucking device has a center case to which a central opening of the disk is inserted; resilient members received within the center case; and claw members for holding the disk in place. The computer system includes a hardware unit to transmit data. 1-10% by weight of a sensitivity enhancing agent, 0. If the skid-type shell is inserted improperly, material may chip off at the edge of the skid-type shell.