A serial axial fan unit includes first and second motors with their base portions, i. The magnetic disk drive or the information processing device, include an unload mechanism moving or evacuating the magnetic head from a surface of the magnetic disk media, and a falling sensor comprising a conductive flexible beam or member having a compatible function, a conductive weight supported by these beams and a conductive wall arranged to be made in contact or non-contact with the weight. The connector has first and second contacts of two kinds. The hydrocyclone includes a housing defining a substantially conical recess having a large diameter end and a small diameter end.